Catadioptric reduction projection optical system

ABSTRACT

A first partial optical system including a first group of lenses having a positive refractive power, a first concave reflection mirror and a second group of lenses having a positive refractive power, for forming a primary reduced image of an object, a second partial optical system including a second concave reelection mirror and a third group of lenses having a positive refractive power, for further reducing the primary reduced image and refocusing it, and a reflection mirror arranged between the first partial optical system and the second partial optical system, for deflecting a light path are arranged in a sequence as viewed from the object. A good image-forming ability as a projection optical system for fabricating a semiconductor device is attained with a simple construction.

This application is a continuation-in-part of application Ser. No. 08/167,209 filed Dec. 16, 1993, (abandoned), which is a continuation-in-part of application Ser. No. 08/095,919 filed Jul. 23, 1993 (abandoned), which is a continuation-in-part of application Ser. No. 08/065,046 filed May 24, 1993 (abandoned), which is a continuation of application Ser. No. 07/918,763 filed Jul. 27, 1992 (abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a catadioptric optical system having a reflection surface and a refraction surface, and more particularly to an image forming optical system for reduction projection.

2. Related Background Art

Various optical systems for projecting and exposing a mask pattern onto a photoresist on a wafer to manufacture an integrated circuit such as an LSI have been proposed. It is known that an aberration is well corrected at a relatively large aperture in a Dyson type catadioptric optical system. However, since a focusing magnification in the Dyson type catadioptric optical system is unity, there is a limit in the transfer of a fine pattern.

As an optical system having a reduction factor suitable for the manufacture of a semiconductor device having a finer pattern, an optical system which is a modification of the Dyson type catadioptric optical system is disclosed U.S. Pat. No. 4,747,678 and U.S. Pat. No. 4,953,960.

The optical system disclosed in U.S. Pat. No. 4,747,678 which permits the reduction projection allows the reduction focusing of a ring-shaped view field. Basically, it comprises three concave mirrors and a convex mirror and is used as a light exposure device for microlithography. Accordingly, it uses a very complex optical construction of a combination of a number of lenses.

The reduction projection optical system disclosed in U.S. Pat. No. 4,953,960 comprises a combination of a concave mirror and a lens system. Since the reduction is attained by one time of focusing, the aberration is large and a combination of a number of lenses is needed to correct the aberration. Since it is essential to provide a large scale beam splitter such as a half mirror in a light path, a loss of light intensity is more than 75% and the increase of exposure time due to the loss of light intensity causes a fatal shortcoming of the reduction of throughput in the manufacturing process of the semiconductor device. Further, a stray light which causes flare and ununiformity in illumination occurs in the large beam splitter in the light path, and it is difficult to manufacture a large semitransparent plane.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a reduction projection optical system which solves problems encountered in the prior art optical system and which is simple in structure and has a good image-forming ability as a projection optical system for use in semiconductor fabrication.

Other objects, features, and effects of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a light path of a first embodiment of a catadioptric reduction projection optical system of the present invention;

FIG. 2 shows a light path of a second embodiment of the present invention;

FIG. 3 shows a light path of a third embodiment of the present invention;

FIG. 4 shows a light path of a fourth embodiment of the present invention;

FIG. 5 shows a light path of a fifth embodiment according to the present invention;

FIG. 6 is a graph showing the coma aberration of the fifth embodiment according to the present invention;

FIG. 7 shows a light path of a sixth embodiment according to the present invention;

FIG. 8 is a graph showing the coma aberration of the sixth embodiment according to the present invention;

FIG. 9 shows a light path of a seventh embodiment according to the present invention;

FIG. 10 is a graph showing the coma aberration of the seventh embodiment according to the present invention;

FIG. 11 shows a light path of an eighth embodiment according to the present invention;

FIG. 12 is a graph showing the coma aberration of the eighth embodiment according to the present invention;

FIG. 13 shows a light path of a ninth embodiment according to the present invention;

FIG. 14 is a graph showing the coma aberration of the ninth embodiment according to the present invention;

FIG. 15 shows a light path of a 10th embodiment according to the present invention;

FIG. 16 is a graph showing the coma aberration of the 10th embodiment according to the present invention;

FIG. 17 shows a light path of an 11th embodiment according to the present invention;

FIG. 18 is a graph showing the coma aberration of the 11th embodiment according to the present invention;

FIG. 19 shows a light path of a 12th embodiment according to the present invention;

FIG. 20 is a graph showing the coma aberration of the 12th embodiment according to the present invention;

FIG. 21 shows a light path of a 13th embodiment of a catadioptric reduction projection optical system of the present invention;

FIG. 22 is a graph showing the coma aberration of the 13th embodiment;

FIG. 23 shows a light path of a 14th embodiment of a catadioptric reduction projection optical system of the present invention;

FIG. 24 is a graph showing the coma aberration of the 14th embodiment;

FIG. 25 shows a light path of a 15th embodiment of a catadioptric reduction projection optical system of the present invention; and

FIG. 26 is a graph showing the coma aberration of the 15th embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A catadioptric reduction projection optical system according to the present invention has, in succession from the object side, a first partial optical system having a lens group G₁ of positive refractive power and a first concave reflecting mirror M₁ for forming the primary reduced image of an object, a second partial optical system having a second concave reflecting mirror M₂ and a lens group G₃ of positive refractive power for further reducing and re-imaging said primary reduced image, and a lens group G₂ disposed near said primary reduced image, and further has a reflecting mirror disposed in the optical path between said first concave reflecting mirror M₁ and said second concave reflecting mirror M₂ for bending the optical path.

In a catadioptric reduction projection optical according to the present invention as described above, the first and second partial optical systems have concave reflecting mirrors that provide considerable refractive power among the total positive refractive power of the entire optical system and a lens group of positive refractive power and both make reduction imaging possible and therefore, a predetermined reduction magnification can be obtained as a whole system without each partial optical system being made to bear a treat burden in aberration correction.

By the lens group G₂ being disposed near the primary reduced image I₁, it becomes possible to apply a reduction magnification more and correct off-axis aberrations better.

Where the lens group G₂ disposed near the primary reduced image I₁ is disposed at the first partial optical system side, it can be considered to be included in the first partial optical system, and where it is positive refractive power disposed immediately forwardly of the primary reduced image, it becomes possible to construct the whole optical system most simply. In this case, the catadioptric reduction projection optical system has, in succession from the object side, a first partial optical system having a first lens group G₁ of positive refractive power, a first concave reflecting mirror M₁ and a second lens group G₂ of positive refractive power and for forming the primary reduced image of an object, and a second partial optical system having a second concave reflecting mirror M₂ and a third lens group G₃ of positive refractive power and for further reducing and re-imaging said primary reduced image, and further has a reflecting mirror disposed in the optical path between the first partial optical system and the second partial optical system for bending the optical path.

In such a construction, the first and second partial optical systems have concave reflecting mirrors that provide considerable refractive power among the total positive refractive power of the entire optical system, and lens groups (a second lens group G₂ and a third lens group G₃) of positive refractive power near the image thereof, whereby both of them make reduction imaging possible and therefore, without each partial optical system being made to bear a great burden in aberration correction, it is possible to be simple in construction and yet maintain an excellent imaging performance.

Further, it is effective to make the construction of the first lens group G₁ into the so-called telephoto type comprising, in succession from the object side, a front group G₁₁ of positive refractive power and a rear group G₁₂ of negative refractive power. In this case, the reduction magnification in the first lens group G₁ can be earned and at the same time, the amount of aberration in the first concave reflecting mirror M₁ can be made small and therefore, it becomes unnecessary to obtain a reduction magnification by the second lens group G₂ and it becomes unnecessary to earn a reduction magnification by the second lens group G₂, and the second lens group G₂ can be used as a lens group exclusively foe aberration correction, and it becomes possible to endow it with a greater numerical aperture (N.A.). Accordingly, the second lens group G₂ can be made into not only a construction which, as described above, earns a reduction magnification with relatively strong refractive power immediately forwardly of the primary reduced image, but also a construction in which the second lens group G₂ is made to function as a lens group exclusively for aberration correction, near the primary reduced image.

Where each concave reflecting mirror is a spherical mirror, it is desirable that in the second partial optical system, a fourth lens group G₄ for aberration correction be disposed between the second concave mirror M₂ and the third lens group G₃. It is also effective to dispose, in the first partial optical system, a fifth lens group G₅ for aberration correction between the first lens group G₁ and the first concave reflecting mirror M₁.

In the manner described above, it is possible to be simple in optical construction and yet maintain an excellent imaging performance, and by having a great numerical aperture (N.A.), the transfer of more minute patterns is possible.

In addition, in an optical system according to the present invention, a plane reflecting mirror M₃ for bending the optical path is disposed in the optical path from-the first partial optical system to the second partial optical system, and preferably between the first concave reflecting mirror M1 and the second concave reflecting mirror M₂, whereby the optical path can be completely separated. Therefore, this reflecting mirror can be a total reflection mirror, and a beam splitter such as a half mirror is not required as is in the aforementioned U.S. Pat. No. 4,953,960. This leads to the advantage that the loss of the quantity of light is much smaller and the possibility of creating harmful stray light such as flare is little.

Also, in an optical system of the present invention, all of the optical members, except the plane reflecting mirror M₃ for bending the optical path, have centers of curvature on the same optical axis.

The essential difference of the construction of the present invention as described above from the optical system disclosed in the aforementioned U.S. Pat. No. 4,747,678 is that a convex reflecting mirror is not required as an optical element. This is because the above-described optical system according to the prior art has adopted a correcting technique whereby negative Petzval sum created by the Concave reflecting mirror is negated by the convex reflecting mirror and the refracting system effects auxiliary aberration correction, whereas the present invention adopts a correcting technique whereby negative Petzval sum created by the concave reflecting mirror is negated by positive Petzval sum in the third lens group G₃ which is a lens group of positive refractive power. Therefore, in the present invention, the positive refractive power of the third lens group G₃ is made considerably strong and is positively used. Where the second lens group G₂ is a lens group of positive refractive power disposed immediately forwardly of the primary reduced image I₁. It is possible to cause the second lens group G₂ to act in addition to the positive refractive power of the third lens group G₃, thereby enhancing the effect,

Features of the present invention are now described in detail. The first and second partial optical systems are reduced image-forming systems as described above but the second concave reflection mirror M₂ in the second partial optical system preferably has a small magnification factor although it is close to unity magnification in order to facilitate the separation of the light path by the planar reflection mirror M₃. Specifically, it is preferable that the following condition is met:

    -1.5<β.sub.M2 <-1.0

where β_(M2) is the magnification of the second concave reflection mirror M₂.

As a result, a position of an object image I₁ by the first partial optical system is closer to the second concave reflection mirror M₂ than a position of an image I₂ by the second partial optical system is so that the interference of the light path is prevented even for a light beam of a large numerical aperture. When β_(M2) exceeds the upper limit, the magnification of the second concave reflection mirror exceeds unity and the separation of the light path is difficult to attain. Conversely, when the magnification exceeds the lower limit, it is difficult for the second partial optical system to attain the desired reduction factor, and the burden of the first partial optical system increases and a complex construction is required to correct the aberration,

The first concave reflection mirror M₁ has a relatively large reduction factor and plays an important role in balancing the compactness of the entire system and the correction of aberration. It is preferable to meet the following condition:

    -0.7<β.sub.M1 <-0.3

where β_(M1) is the magnification of the first concave reflection mirror M₁.

The balance of aberration of the groups of lenses is now discussed, The first group of lenses G₁ is arranged in the vicinity of the object surface and functions as a so-called view field lens and also corrects direction aberration. The second and third groups of lenses G₂ and G₃ have large positive refractive powers as described above, contribute to the formation of the reduced image and positively function to correct the Petzval sum, and the negative distortion aberration generated therein is corrected by the positive distortion aberration of the first group of lenses G₁. The fourth group of lenses G₄ provisionally arranged in the second partial optical system is effective to correct higher order spherical aberration. Where the concave reflection mirrors, particularly the first concave reflection mirror M₁ which shares a large portion of the reduction factor are non-spherical rather than spherical, the fourth group of lenses G₄ may be omitted.

A catadioptric reduction projection optical system according to the present invention has a first partial optical system including, in succession from the object side, a first lens group G₁ of positive refractive power and a first concave reflecting (or reflection) mirror M₁ for forming a primary reduced image of an object, and a second partial optical system including, in succession from the object side, a second concave reflection mirror M₂ and a third lens group G₃ of positive refractive power for re-imaging the primary reduced image, and a second lens group G₂ of positive or negative refractive power is arranged in the optical path (or light path) between the first and second concave reflection mirrors M₁ and M₂.

In a catadioptric reduction projection optical system according to the present invention with the above-mentioned construction, the first and second partial optical systems have concave reflection mirrors that provide considerable refractive power among the total positive refractive power of the entire optical system and a lens group (first or third lens group G₁ or G₃) of positive refractive power, and both make reduction imaging possible. Therefore, a predetermined reduction factor can be obtained as a whole system without forcing a partial optical system to bear a great burden in aberration correction. For this reason, it is possible to simplify the optical construction and yet maintain an excellent imaging performance.

The balance of aberration of the lens groups in a catadioptric reduction projection optical system according to the present invention will now be discussed. The first lens group G₁ is arranged in the vicinity of the object surface, has a function of maintaining telecentric characteristics, and corrects distortion. The second and third lens groups G₂ and G₃ contribute to formation of the reduced image and to correction of the Petzval sum. In particular, the second lens group G₂ functions as a so-called field lens, and allows a light beam from a position near the optical axis of the first concave reflection mirror M₁ to pass therethrough. Thus, the light beam through second concave mirror M₂ at a position near the optical axis and generation of aberration in the second concave reflection mirror M₂ can be prevented. The negative distortion generated in the second and third lens groups G₂ and G₃ is corrected by the positive distortion of the first lens group G₁. Lens groups (fourth and fifth lens groups G₄ and G₅) provisionally disposed in the vicinity of the concave reflection mirrors are effective to correct higher order spherical aberration generated by the concave reflection mirrors. When the concave reflection mirror is constituted to be a non-spherical mirror, since aberration generated by the concave reflection mirror is minimized, the fourth and fifth lens groups G₄ and G₅ may be omitted.

The characteristic features of the construction according to the present invention will be described in detail below.

It is preferable that a catadioptric reduction projection optical system according to the present invention be arranged to satisfy the following condition:

    -2.5<β.sub.M2 <-0.7                                   (1)

where β_(M2) is the magnification of the second concave reflection mirror M₂. The condition (1) defines a preferable magnification of the second concave reflection mirror M₂. When β_(M2) exceeds the upper limit of the condition (1), the refractive power of the concave reflection mirror M₂ increases, aberrations, especially spherical aberration and coma, generated by the concave reflection mirror M₂ increase, and it becomes difficult to satisfactorily correct the aberrations. Furthermore, a light beam propagating toward the concave reflection mirror M₂ considerably overlaps a light beam propagating from the concave reflection mirror M₂ toward the secondary image surface, and it becomes difficult to obtain a physically constructible optical system. When β_(M2) is set below the lower limit, the refractive power of the concave reflection mirror M₂ decreases, and the decrease in refractive power must be compensated for by a refracting optical system, thus losing the merits of a reflecting optical system. At this time, the construction of the refracting optical system is more complicated, and aberration correction becomes harder to attain.

Furthermore, in order to facilitate separation of the light path by a planar reflection mirror (plane reflection mirror) in the catadioptric reduction projection optical system according to the present invention, it is further preferable to satisfy the following condition:

    -1.5<β.sub.M2 <-1.0

where β_(M2) is the magnification of the second concave reflection mirror M₂. Under this condition, when both the first and second optical systems are reduction imaging systems, since the position of an object image (primary image) I₁ formed by the first partial optical system becomes closer to the second concave reflection mirror M₂ than the position of an image I₂ formed by the second partial optical system, the interference of the light path can be prevented for a light beam of a large numerical aperture. When β_(M2) exceeds the upper limit of this condition, since the magnification of the second concave reflection mirror M₂ exceeds unity, the separation of the light path may become difficult to attain. Conversely, when the magnification decreases beyond the lower limit of the condition, it is difficult for the second partial optical system to attain a desired reduction factor, and the burden of the first partial optical system increases, thus requiring a complicated construction for aberration correction.

It is preferable that a catadioptric reduction projection optical system according to the present invention be arranged to satisfy the following condition:

    -2.0<β.sub.M1 <-0.3                                   (2)

where β_(M1) is the magnification of the first concave reflection mirror. This condition defines a proper magnification of the first concave reflection mirror M₁. When β_(M1) exceeds the upper limit of the condition (2), the refractive power of the first concave reflection mirror M₁ increases, and aberrations, especially spherical aberration and coma, generated by the first concave reflection mirror M₁ increase. Thus, the negative refractive power of a refracting optical system must be strengthened to cancel these aberrations, and it becomes difficult to satisfactorily correct aberrations. When the magnification is set below the lower limit of the condition (2), the refractive power of the refracting optical system must be strengthened to compensate for the refractive power of the concave reflection mirror M₁. At this time, the merits of a reflecting optical system are lost, the construction of the refracting optical system is more complicated, and aberration correction becomes harder to attain.

With the above-mentioned construction, a catadioptric reduction projection optical system according to the present invention preferably satisfies the following condition:

    0.05<β.sub.G3 <0.6                                    (3)

where β_(G3) is the magnification of the third lens group G₃ of positive refractive power. This condition defines a proper magnification of the third lens group G₃, and allows for realization of a catadioptric reduction projection optical system having an excellent optical performance, and allows for obtaining a physically constructible catadioptric reduction projection optical system. The physically constructible optical system means an optical system in which optical members do not interfere with each other in an arrangement of optical members constituting the catadioptric reduction projection optical system.

When β_(G3) exceeds the upper limit of the above-mentioned condition (3), a light beam propagating between the concave reflection mirrors M₁ and M₂ considerably overlaps a light beam propagating from the concave reflection mirror M₂ to the secondary image surface, and the arrangement of optical members constituting the catadioptric reduction protection optical system cannot be realized. When β_(G3) is set below the lower limit of the above-mentioned condition (3), the refractive power of the third lens group G₃ increases, and coma and chromatic aberration are generated considerably.

In a catadioptric reduction projection optical system according to the present invention, it is preferable that at least one of the first to third lens groups G₁ to G₃ be constituted by at least two different glass materials. Then, chromatic aberration can be satisfactorily corrected, and an imaging performance can be further improved. In particular, this construction is effective when a light source having a predetermined wavelength width is used.

It is preferable that a catadioptric reduction projection optical system according to the present invention have at least two planar reflection mirrors. With this construction, the object surface and the image surface can be set to be parallel to each other.

In order to achieve the above objects, there is provided a catadioptric reduction projection optical system according to another aspect of the present invention comprising:

a first partial optical system for forming a primary image of the object; and

a second partial optical system for forming a secondary image of the object based on light from the primary image,

the first partial optical system having a first lens group of positive refractive power, a second lens group of negative refractive power, and a first concave reflection mirror in succession from a light incident side, and

the second partial optical system having a second concave reflection mirror, and a fourth lens group of positive refractive power,

wherein a third lens group of positive or negative refractive power is disposed in a light path between the first concave reflection mirror and the second concave reflection mirror,

the first to fourth lens groups consist of at least one material selected from the group consisting of quartz glass and fluorite, and

a magnification factor β_(M1) of the first concave reflection mirror and a magnification factor β_(M2) of the second concave reflection mirror meet conditions of:

    -1.0<β.sub.M1 <-0.7

    -2.5<β.sub.M2 <-1.2.

In order to satisfactorily correct other aberrations while correcting chromatic aberration in a wide bandwidth and providing a large numerical aperture, it is preferable that not only the refractive power of the reflection mirror but also that of a refractive member be strengthened. Therefore, it is preferable that the refractive member be constituted by two kinds of glass, i.e., fluorite and quartz glass. When the wavelength used for a light source is at a short wavelength side, and particularly is 250 nm or less, an advantage can be obtained in terms of a transmittance.

A catadioptric reduction projection optical system according to still another aspect of the present invention satisfies the following condition:

    -1.0<β.sub.M1 <-0.7                                   (4)

where β_(M1) is the magnification of the first concave reflection mirror. This condition defines a proper magnification factor of the first concave reflection mirror, and allows for realization of a catadioptric reduction projection optical system having an excellent optical performance, and allows for obtaining a physically constructible catadioptric reduction projection optical system. The physically constructible optical system means an optical system in which optical members do not interfere with each other in an arrangement of optical members constituting the catadioptric reduction projection optical system.

When β_(M1) exceeds the upper limit of the above-mentioned condition (4), the refractive power of the first concave reflection mirror increases, and aberrations, especially, spherical aberration and coma, generated by the first concave reflection mirror increase. In order to cancel these aberrations, the negative refractive power of a refracting optical system must be strengthened, and it becomes difficult to satisfactorily correct these aberrations. For this reason, the upper limit of β_(M1) is set to -0.8. When β_(M1) is set below the lower limit of the condition (4), the refractive power of the refracting optical system must compensate for a decrease in refractive power of the first concave reflection mirror. It is not preferable to further complicate the construction of the refracting optical system due to correction of aberrations. As for the chromatic aberration, since each lens group of a refractive system achieves achromatism, this operation complicates the refractive system more. At the same time, coma is generated due to an increase in secondary spectrum and its color, and it is difficult to correct the coma. Therefore, it is preferable that the lower limit of β_(M1) be set to -1.0.

A catadioptric reduction projection optical system according to still another aspect of the present invention satisfies the following condition:

    -2.5<β.sub.M2 <-1.2                                   (5)

where β_(M2) is the magnification of the second concave reflection mirror. This condition defines a proper magnification factor of the second concave reflection mirror, and allows for the realization of a catadioptric reduction projection optical system having an excellent optical performance, and allows for obtaining a physically constructible catadioptric reduction projection optical system.

When β_(M2) exceeds the upper limit of the above-mentioned condition (5), the refractive power of the second concave reflection mirror increases, and aberrations, especially, spherical aberration and coma, generated by the second concave reflection mirror increase. In order to cancel these aberrations, the negative refractive power of a refracting optical system must be strengthened, and it becomes difficult to satisfactorily correct these aberrations. For this reason, the upper limit of β_(M2) is preferably set to -1.5.

When β_(M2) is set below the lower limit of the condition (5), the refractive power of the refracting optical system must compensate for a decrease in refractive power of the second concave reflection mirror. It is not preferable to further complicate the construction of the refracting optical system due to correction of aberrations. As for the chromatic aberration, since each lens group of a refractive system achieves achromatism, this operation complicates the refractive system more. At the same time, coma is generated due to an increase in secondary spectrum and its color, and it is difficult to correct the coma. Therefore, it is more preferable that the lower limit of β_(M2) be set to -2.3.

A catadioptric reduction projection optical system according to still another aspect of the present invention preferably satisfies the following condition:

    0.05<β.sub.G4 <0.3                                    (6)

where β_(G4) is the magnification of the fourth lens group G₄ having positive refractive power. This condition defines a proper magnification factor of the fourth lens group G₄, and allows for realization of a catadioptric reduction projection optical system having an excellent optical performance, and allows for obtaining a physically constructible catadioptric reduction projection optical system. When β_(M4) exceeds the upper limit of the above-mentioned condition (6), the refractive power of the fourth lens group G₄ decreases, and an optical system disposed in a light path before the fourth lens group G₄ compensates for a decrease in refractive power of the fourth lens group G₄. In particular, the first and second concave reflection mirrors tend to compensate for the refractive power of the fourth lens group G₄, and aberrations generated by the first and second concave reflection mirrors cannot be corrected. Further, light beams before and after incidence on the second concave reflection mirror or lenses at incident and exit sides tend to interfere with each other, and it becomes difficult to achieve a constructible optical arrangement. Taking this problem into consideration, it is more preferable that the upper limit of β_(G4) be set to 0.2.

When β_(G4) is set below the lower limit of the condition (6), the refractive power of the second concave reflection mirror increases, and aberrations, especially, spherical aberration and coma, generated by the fourth lens group G₄ increase. As for the chromatic aberration, since each lens group of a refractive system achieves achromatism, this operation complicates the refractive system more. At the same time, coma is generated due to an increase in secondary spectrum and its color, and it is difficult to correct the coma. Therefore, it is more preferable that the lower limit of β_(G4) be set to 0.1. The balance of aberration of the lens groups in the catadioptric reduction projection optical system according to still another aspect of the present invention will now be discussed. The first lens group is arranged in the vicinity of the object, has a function of maintaining telecentric characteristics, and corrects distortion. The second lens group mainly corrects spherical aberration and coma generated by a concave reflection mirror and convex lens groups. The third and fourth lens groups contribute to formation of the reduced image and to correction of the Petzval sum. In particular, the third lens group functions as a so-called field lens, and allows a light beam from a position near the optical axis of the first concave reflection mirror to pass therethrough. With this construction, the light beam passes near the optical axis of the second concave reflection mirror. Thus, any aberration in the second concave reflection mirror can be prevented.

Preferred embodiments of the present invention are now explained. FIG. 1 shows light path for a first embodiment of the present invention. As shown, a light beam from an object surface passes through a first group of lenses G₁ comprising a biconvex positive lens L₁₁ and a negative meniscus lens L₁₂ having a convex surface thereof facing the object, is directed to a first concave reflection mirror M₁ where it is reflected and reduced by a factor β_(M1), and is directed to a second group of lenses G₂ comprising a negative meniscus lens L₂₁ having a convex-surface thereof facing the first concave reflection mirror M₁ and a positive lens L₂₂ having a stronger radius of curvature on a surface facing the first concave reflection mirror M₁. It is further reduced by the second group of lenses G₂ to form a primary image I₁. The light beam from the primary image I₁ is reflected by the light path deflecting planar reflection mirror M₃, directed to a second concave reflection mirror M₂ and is reflected thereby so that it is magnified by a factor which is slightly larger than unity. It is reduced by a third group of lenses G₃ comprising a positive lens L₃₁ having a stronger radius of curvature or a surface facing the second concave reflection mirror M₂, a meniscus lens L₃₂ having a convex surface facing the second concave reflection mirror M₂ and a positive lens L₃₃ having a stronger radius of curvature on a surface facing the second concave reflection mirror M₂ so that a secondary image I₂ which is reduction of the primary image I₁ is formed. A negative lens having a weak negative refractive power is arranged, as a fourth group of lenses G₄, between the second concave reflection mirror M₂ and the third group of lenses G₃, to correct higher order spherical aberration.

In the above construction, the first group of lenses G₁, the first concave reflection mirror M₁ and the second group of lenses G₂ form the first partial optical system, the second concave reflection mirror M₂, the third group of lenses G₃ and the fourth group of lenses G₄ form the second partial optical system. The second group of lenses G₂ in the first partial optical system is provided on only one side of an optical axis Ax1 of the first partial optical system so that it does not interrupt the light beam directed to the first concave reflection mirror M₁ and condenses only the reflected light from the light concave reflection mirror M₁. The light path deflecting planar reflection mirror M₃ is obliquely arranged at an angle of 45° to the optical axis Ax1 of the first partial optical system in the vicinity of the third group of lenses G₃, and the optical axis Ax2 of the second partial optical system is orthogonal to the optical axis Ax1 of the first partial optical system. Since the planar reflection mirror M₃ is arranged in the vicinity of the primary image I₁, more specifically exit light side vicinity of the primary image I₁, the dimension thereof is small and it can be arranged by cutting off a portion of the first positive lens L₃₁ in the third group of lenses G₃. The fourth group of lenses G₄ in the second partial optical system is arranged not to interrupt the light path of the first partial optical system. While the angle of inclination of the planar reflection mirror M₃ is 45° in the present embodiment, it may be any angle so long as the separation of the light path is attained.

The first embodiment has a reduction factor of +0.25 or 1/4 as a while and a numerical aperture (N.A.) of 0.4 in a ring-shaped view field centered at an arc having a radius of 25 mm from the optical axis.

Data of the first embodiment is shown in a table below, in which signs of the refractive index and the plane-to-plane distance are reversed by the reflection by the concave reflection mirror. The position of the third reflection mirror M₃ for deflecting the light path is omitted since it is not essential in the optical design.

                  TABLE 1                                                          ______________________________________                                         Data of First Embodiment                                                                          Plane-to-                                                          Radius of   Plane    Refractive                                         No.    Curvature   Distance Index                                              ______________________________________                                                (Object     47.063   1.000                                                     Plane)                                                                  1      677.873     25.000   1.500    L.sub.11 G.sub.1                          2      -988.280    22.657   1.000                                              3      591.515     25.020   1.500    L.sub.12                                  4      288.196     990.000  1.000                                              5      -744.372    -479.502 -1.000   M.sub.1                                   6      -131.046    -12.701  -1.500   L.sub.21 G.sub.2                          7      -83.678     -3.000   -1.000                                             8      -88.873     -53.909  -1.500   L.sub.22                                  9      742.557     -250.755 -1.000                                             10     2588.139    -20.000  -1.500   G.sub.4                                   11     -24840.890  -376.150 -1.000                                             12     681.247     376.150  1.000    M.sub.2                                   13     -24840.890  20.000   1.500    G.sub.4                                   14     2588.139    203.875  1.000                                              15     277.553     16.500   1.500    L.sub.31 G.sub.3                          16     621.605     0.0500   1.000                                              17     103.075     61.334   1.500    L.sub.32                                  18     74.101      5.000    1.000                                              19     81.631      54.747   1.500    L.sub.33                                  20     461.143     9.946    1.000                                                          β.sub.M2 = 1.18                                                           β.sub.M1 = -0.55                                                          β.sub.G3 = 0.501                                              ______________________________________                                    

A second embodiment of the present invention shown in FIG. 2 is basically same as the first embodiment but the overall optical system is more compact and the first and second concave reflection mirrors M₁ and M₂ are arranged closer to the object surface 0 and the secondary image I₂ and the diameters thereof are smaller. In order to correct the aberrations generated by the compaction, a meniscus lens having a convex surface thereof facing the first concave reflection mirror M₁ is arranged as a fifth group of lenses G₅ between the first concave reflection mirror M₁ and the second group of lenses G₂ and a biconvex positive lens L₁₁, a meniscus lens L₁₂ having a concave surface thereof facing the object surface and a meniscus lens L₁₃ having a convex surface thereof facing the object surface are provided as the first group of lenses G₁.

The second embodiment has a reduction factor of +0.25 or 1/4 as a whole and a numerical aperture (N.A.) of 0.4 in a ring-shaped view field centered at an arc having a radius of 25 mm from the optical axis.

Data of the second embodiment is shown in a table below.

                  TABLE 2                                                          ______________________________________                                         Data of Second Embodiment                                                                         Plane-to-                                                          Radius of   Plane    Refractive                                         No.    Curvature   Distance Index                                              ______________________________________                                                (Object     112.472  1.000                                                     Plane)                                                                  1      977.575     30.000   1.500    L.sub.11 G.sub.1                          2      -1030.934   15.000   1.000                                              3      -1446.147   20.000   1.500    L.sub.12                                  4      -1878.184   0.500    1.000                                              5      316.624     30.000   1.500    L.sub.13                                  6      289.149     613.035  1.000                                              7      -407.188    20.000   1.500    G.sub.5                                   8      -469.137    226.192  1.000                                              9      -692.557    -226.192 -1.000   M.sub.1                                   10     -469.137    -20.000  -1.500   G.sub.5                                   11     -407.188    -182.064 -1.000                                             12     -6117.578   -20.000  -1.500   L.sub.21 G.sub.2                          13     3775.716    -0.500   -1.000                                             14     -136.376    -71.120  -1.500   L.sub.22                                  15     881.988     -212.075 -1.000                                             16     2473.277    -20.000  -1.500   G.sub.4                                   17     -44915.848  -371.392 -1.000                                             18     608.000     371.392  1.000    M.sub.2                                   19     -44915.848  20.000   1.500    G.sub.4                                   20     2473.277    125.565  1.000                                              21     254.431     17.000   1.500    L.sub.31 G.sub.3                          22     452.400     0.010    1.000                                              23     94.027      46.970   1.500    L.sub.32                                  24     69.588      5.000    1.000                                              25     76.436      51.600   1.500    L.sub.33                                  26     458.225     11.117   1.000                                                          β.sub.M2 = -1.26                                                          β.sub.M1 = -0.52                                                          β.sub.G3 = 0.539                                              ______________________________________                                    

In a third embodiment of the present invention, as shown in FIG. 3, the first lens group G₁ is comprised of a front group G₁₁ of positive refractive power having a positive lens L₁₁ having its surface of sharper curvature facing the image side and a positive meniscus lens L₁₂ having its convex surface facing the object side, and a rear group G₁₂ of negative refractive power having a biconcave negative lens L₁₃ and a positive lens L₁₄ having its surface of sharper curvature facing the image side. A reduction magnification can be provided by the first lens group G₁ constituting such a telephoto type and therefore, it becomes unnecessary to provide a reduction magnification in the second lens group G₂, which is comprised of a negative lens L₂₁ disposed immediately forwardly of the primary reduced image I₁, a positive lens L₂₂ disposed immediately rearwardly of the primary reduced image I₁ and a meniscus lens L₂₃ having its concave surface facing the primary reduced image I₁ side, and it is possible to effect the correction of off-axis aberrations well. Therefore, it becomes possible to make the numerical aperture (N.A.) greater.

The functions of the first concave reflecting mirror M₁, the plane reflecting mirror M₃ for bending the optical path and the second concave reflecting mirror M₂ are substantially similar to those in the previously described embodiment, and the second concave reflecting mirror M₂ also has a magnification somewhat greater than one-to-one magnification. The third lens group G₃ is of a somewhat more complicated construction than the previous embodiment in order to effect good aberration correction for a greater numerical aperture. That is, a reduction magnification is given by the third lens group G₃ comprising two biconvex positive lenses L₃₁, L₃₂, a biconcave negative lens L₃₃, a positive lens L₃₄ having its surface of sharper curvature facing the second concave reflecting mirror M₂ side, a negative lens L₃₅ having its surface of sharper curvature facing the image side, and a positive lens L₃₆ having its surface of sharper curvature facing the second concave reflecting mirror M₂ side, and there is formed a secondary image I₂ more reduced than the primary image I₁. Again in this embodiment, a negative lens having weak negative refractive power as the fourth lens group G₄ is disposed between the second concave reflecting mirror M₂ and the third lens group G₃, whereby spherical aberration of high orders are corrected well.

In the construction of this third embodiment, the first lens group G₁, the first concave reflecting mirror M₁ and the negative lens L₂₁ in the second lens group G₂ can be regarded as constituting a first partial optical system, and the positive lens L₂₂ and the meniscus lens L₂₃ having its concave surface facing the primary reduced image I₁ side in the second lens group G₂, the second concave reflecting mirror M₂, the third lens group G₃ and the fourth lens group G₄ can be regarded as constituting a second partial optical system. On the other hand, the first lens group G₁ and the first concave reflecting mirror M₁ can be regarded as constituting the first partial optical system, the second concave reflecting mirror M₂, the third lens group G₃ and the fourth lens group G₄ can be regarded as constituting the second partial optical system, and relative to these, the second lens group G₂ for aberration correction can be regarded as being disposed near the primary reduced image I₁.

The rear group G₁₂ in the first lens group G₁ is provided only on one side of the optical axis Ax1 of the first partial optical system to make only the light travelling toward the first concave reflecting mirror M₁ diverge without intercepting the reflected light beam from the first concave reflecting mirror M₁. Also, the plane reflecting mirror M₃ for bending the optical path is obliquely disposed near the third lens group G₃ at an angle of 45° with respect to the optical axis Ax1 of the first partial optical system, and the optical axis Ax2 of the second partial optical system is made orthogonal to the optical axis Ax1 of the first partial optical system. This plane reflecting mirror M₃, as in the previously described embodiment, is near the primary image I₁ and therefore the size thereof is small, and this mirror can be installed in the space near the third lens group G₃.

Since the optical path of the second partial optical system is disposed between the front group G₁₁ and rear group G₁₂ in the first lens group G₁, the whole optical system can be made compact without waste of space. Also, of course, as in the previous embodiment, the fourth lens group G₄ in the second partial optical system is provided so as not to interrupt the optical path of the first partial optical system.

Again this third embodiment has a reduction magnification +0.25 i.e., a reduction rate of one fourth, as a whole, and secures a zonal field of view having a radius of 25 mm from the optical axis, but has a great numerical aperture (N.A.) of 0.45.

The numerical data of the third embodiment are shown in a table below. In the table, it is to be understood that the signs of the refractive indices and the inter-surface spacings are reversed by the reflection on the concave reflecting mirror, and again here, the location of the third reflecting surface M₃ for bending the optical path is not essential in optical design and therefore is omitted.

                  TABLE 3                                                          ______________________________________                                         Numerical Data of the Third Embodiment                                                            Inter-                                                             Radius of   surface  Refractive                                         No.    Curvature   Distance Index                                              ______________________________________                                                (Object     179.407  1.000                                                     surface)                                                                1      3465.978    30.000   1.501    L.sub.11 G.sub.11 G.sub.1                 2      -528.018    0.100    1.000                                              3      261.503     31.759   1.501    L.sub.12                                  4      390.000     316.878  1.000                                              5      -354.698    17.000   1.501    L.sub.13 G.sub.12                         6      255.219     11.599   1.000                                              7      1186.851    25.883   1.501    L.sub.14                                  8      -281.461    580.467  1.000                                              9      -766.948    -589.210 -1.000   M.sub.1                                   10     243.085     -14.000  -1.501   L.sub.21 G.sub.2                          11     3114.038    -50.454  -1.000                                             12     -3513.309   -22.000  -1.501   L.sub.22                                  13     253.255     -8.618   -1.000                                             14     169.996     -20.000  -1.501   L.sub.23                                  15     230.045     -270.073 -1.000                                             16     642.510     -23.000  -1.501   G.sub.4                                   17     1268.362    -277.914 -1.000                                             18     659.079     277.914  1.000    M.sub.2                                   19     1268.362    23.000   1.501    G.sub.4                                   20     642.510     208.073  1.000                                              21     340.589     16.500   1.501    L.sub.31 G.sub.3                          22     -716.211    20.500   1.000                                              23     150.058     26.000   1.501    L.sub.32                                  24     -323.551    1.320    1.000                                              25     -261.398    9.000    1.501    L.sub.33                                  26     209.855     0.500    1.000                                              27     108.115     34.184   1.501    L.sub.34                                  28     -724.878    0.500    1.000                                              29     469.777     9.000    1.501    L.sub.35                                  30     70.411      1.400    1.000                                              31     77.096      34.266   1.501    L.sub.36                                  32     -720.000    15.100   1.000                                                          β.sub.M2 = -1.16                                                          β.sub.M1 = -0.57                                                          β.sub.G3 = 0.3275                                             ______________________________________                                    

In a fourth embodiment of the present invention, as shown in FIG. 4, the construction of the first lens group G₁ is basically similar to that in the third embodiment, but the second lens group G₂ is comprised of a positive lens L₂₁ and a biconcave negative lens L₂₂ disposed immediately rearwardly of the primary reduced image I₁, and no lens is present immediately forwardly of the primary reduced image I₁, i.e., between the first concave reflecting mirror M₁ adjacent to the first partial optical system and the primary reduced image I₁. In this embodiment, a reduction magnification is provided and aberration correction is sufficiently done in the first lens group G₁ comprising a front group G₁₁ of positive refractive power and a rear group G₁₂ of negative refractive power and therefore, the construction of the second lens group G₂ can be made simple.

The constructions of the other lens groups in this embodiment are substantially similar to those in the third embodiment.

Again this fourth embodiment has a reduction magnification +0.25, i.e., a reduction rate of one fourth, as a whole, and has a great numerical aperture (N.A.) of 0.45 in a zonal field of view having a radius of 25 mm from the optical axis.

The numerical data of the fourth embodiment are shown in Table 4 below.

                  TABLE 4                                                          ______________________________________                                         Numerical Data of the Fourth Embodiment                                                           Inter-                                                             Radius of   surface  Refractive                                         No.    Curvature   Distance Index                                              ______________________________________                                                (Object     187.568  1.000                                                     surface)                                                                1      1446.067    30.000   1.501    L.sub.11 G.sub.11 G.sub.1                 2      -640.000    0.100    1.000                                              3      274.000     31.759   1.501    L.sub.12                                  4      390.000     345.240  1.000                                              5      -338.360    17.000   1.501    L.sub.13 G.sub.12                         6      273.442     7.464    1.000                                              7      590.613     25.883   1.501    L.sub.14                                  8      -281.411    589.287  1.000                                              9      -831.145    -656.955 -1.000   M.sub.1                                   10     180.000     -23.000  -1.501   L.sub.21 G.sub.2                          11     -2908.427   -5.005   -1.000                                             12     -429.596    -18.000  -1.501   L.sub.22                                  13     197.384     -292.451 -1.000                                             14     380.443     -23.000  -1.501   G.sub.4                                   15     596.210     -294.291 -1.000                                             16     653.346     294.291  1.000    M.sub.2                                   17     596.210     23.000   1.501    G.sub.4                                   18     380.443     222.451  1.000                                              19     153.779     17.000   1.501    L.sub.31 G.sub.3                          20     689.474     0.500    1.000                                              21     156.334     26.500   1.501    L.sub.32                                  22     -680.839    0.822    1.000                                              23     -508.366    9.000    1.501    L.sub.33                                  24     391.014     0.500    1.000                                              25     143.155     29.818   1.501    L.sub.34                                  26     485.639     0.500    1.000                                              27     267.611     9.000    1.501    L.sub.35                                  28     65.131      1.400    1.000                                              29     66.963      28.952   1.501    L.sub.36                                  30     -844.417    15.100   1.000                                                          β.sub.M2 = -1.17                                                          β.sub.M1 = -0.55                                                          βG.sub.3 = 0.3562                                             ______________________________________                                    

In the above embodiments, the first concave reflection mirror M₁ and the second concave reflection mirrors M₂ are spherical although they may be non-spherical such as oval. In this case, the fourth group of lenses G₄ may be omitted as described above.

In the catadioptric reduction projection optical systems according to the first to fourth embodiments, the first concave reflection mirror M₁ has a relatively large reduction factor and plays an important role in balancing the compactness of the entire system and the correction of aberration. Thus, in the first to fourth embodiments, it is preferable to satisfy:

    -0.7<β.sub.M1 <-0.3

where β_(M1) is the magnification of the first concave reflection mirror M₁.

FIG. 5 Shows a light path construction according to the fifth embodiment of the present invention. As shown in FIG. 5, a light beam from an object surface passes through a first lens group G₁ which comprises a biconvex positive lens L₁₁, a positive meniscus lens L₁₂ having a convex surface facing the object side, and a negative meniscus lens L₁₃ having a convex surface facing the object side, and has positive refractive power as a whole, and is reflected by a first concave reflection mirror M₁ having a magnification slightly smaller than unity. Then, the light path is bent by a planar reflection mirror M₃. The first lens group G₁ mainly functions to correct distortion and to maintain telecentric characteristics. The first lens group G₁ and the first concave reflection mirror M₁ form a primary reduced image I₁.

A light beam from the primary image I₁ passes through a second lens group G₂ comprising a positive meniscus lens L₂₁ having a convex surface facing the primary image side, a negative meniscus lens L₂₂ having a concave surface facing the primary image side, and a biconvex positive lens L₂₃, and reaches a second concave reflection mirror M₂ having an enlargement factor via a fourth lens group G₄ having negative refractive power. The second lens group G₂ mainly functions to correct distortion and curvature of field, and functions as a field lens. The fourth lens group G₄ comprises a negative meniscus lens having a convex surface facing the second concave reflection mirror M₂ side, and functions to correct aberrations caused by the first and second concave reflection mirrors M₁ and M₂.

The light beam reflected by the second concave reflection mirror M₂ passes through the fourth lens group G₄ again, and then becomes incident on a third lens group G₃ having positive refractive power. The third lens group G₃ comprises, in succession from the incident side of a light beam, a negative meniscus lens L₃₁ having a concave lens facing the incident side, a positive meniscus lens L₃₂ having a convex surface facing the incident side, a positive meniscus lens L₃₃ having a convex surface facing the incident side, a biconcave negative lens L₃₄, a biconvex positive lens L₃₅, a positive meniscus lens L₃₆ having a convex surface facing the incident side, and a positive meniscus lens L₃₇ having a convex surface facing the incident side. The third lens group G₃ has a positive Petzval sum to cancel the function of making the Petzval sum by the first and second concave reflection mirrors M₁ and M₂ negative. The third lens group G₃ forms a second image I₂ in a larger reduction scale than that of the primary image I₁.

In the above-mentioned construction, the first lens group G₁ and the first concave reflection mirror M₁ constitute a first partial optical system, and the second concave reflection mirror M₂ and the third lens group G₃ constitute a second partial optical system. The second lens group G₂ is disposed in the light path between the first and second concave reflection mirrors M₁ and M₂. The planar reflection mirror M₃ for bending the light path is obliquely disposed near the first lens group G₁ at an angle of 45° with respect to an optical axis Ax₁ of the first partial optical system, so that an optical axis Ax₂ of the second partial optical system extends perpendicular to the optical axis Ax₁ of the first partial optical system. The second lens group G₂ is disposed on only one side of the second partial optical system so as to focus light reflected by the first concave reflection mirror M₁ without shielding a light beam propagating toward the second concave reflection mirror M₂.

The fifth embodiment has a reduction factor of +0.20 or 1/5 as a whole, and achieves a numerical aperture of (N.A.) of 0.45 in a ring-shaped view field centered at an arc having a radius of 20 mm from the optical axis.

Data of the fifth embodiment is shown in Table 5 below.

In Table 5, the signs of the refractive index and the plane-to-plane distance are reversed by reflection by the concave reflection mirror. The refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrF. Note that the position of the planar reflection mirror M₃ for bending the light path is omitted since it is not essential in the optical design.

                  TABLE 5                                                          ______________________________________                                         Data of Fifth Embodiment                                                                       Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   256.414   1.0000                                                     Surface)                                                                 1     571.882   35.000    1.50890 (quartz)                                                                               L.sub.11                             2     -1107.127 13.569    1.0000                                               3     286.383   38.000    1.50890 (quartz)                                                                               L.sub.12                             4     2061.034  143.443   1.0000                                               5     323.826   20.000    1.50890 (quartz)                                                                               L.sub.13                             6     134.427   535.000   1.0000                                               7     -816.864  -800.000  -1.0000         M.sub.1                              8     -435.732  -25.000   -1.50890                                                                               (quartz)                                                                               L.sub.21                             9     -664.126  -96.462   -1.0000                                              10    231.231   -25.000   -1.50890                                                                               (quartz)                                                                               L.sub.22                             11    750.143   -107.120  -1.0000                                              12    -622.742  -59.000   -1.50890                                                                               (quartz)                                                                               L.sub.23                             13    723.951   -616.105  -1.0000                                              14    259.861   -25.000   -1.50890                                                                               (quartz)                                                                               G.sub.4                              15    891.669   -28.536   -1.0000                                              16    537.817   28.536    1.0000          M.sub.2                              17    891.669   25.000    1.50890 (quartz)                                                                               G.sub.4                              18    259.861   602.523   1.0000                                               19    -1642.894 12.745    1.50890 (quartz)                                                                               L.sub.31                             20    -356.710  2.000     1.0000                                               21    166.981   32.465    1.50890 (quartz)                                                                               L.sub.32                             22    -4368.603 0.201     1.0000                                               23    188.353   14.825    1.50890 (quartz)                                                                               L.sub.33                             24    489.910   10.157    1.0000                                               25    -401.443  10.220    1.50890 (quartz)                                                                               L.sub.34                             26    370.153   3.669     1.0000                                               27    1112.370  53.780    1.50890 (quartz)                                                                               L.sub.35                             28    -387.055  0.100     1.0000                                               29    106.932   70.805    1.50890 (quartz)                                                                               L.sub.36                             30    329.200   0.100     1.0000                                               31    153.221   12.340    1.50890 (quartz)                                                                               L.sub.37                             32    983.363   10.000    1.0000                                               33    (Image                                                                         Surface)                                                                         <Condition Corresponding Values>                                               β.sub.M2 = -1.225                                                         β.sub.M1 = -0.8606                                                        β.sub.G3 = 0.0761                                                 ______________________________________                                    

FIG. 6 shows coma for explaining the imaging performance of the fifth embodiment. FIG. 6 shows coma in the meridional direction at the center of the ring-shaped view field. As can be seen from FIG. 6, this embodiment maintains an excellent imaging performance.

As shown in FIG. 7, in a sixth embodiment according to the present invention, a light beam from the object surface passes through a first lens group G₁ which comprises a biconvex positive lens L₁₁, a positive meniscus lens L₁₂ having a convex surface facing the incident side of the light beam, and a negative meniscus lens L₁₃ having a convex surface facing the incident side, and has positive refractive power as a whole, and is then reflected by a first concave reflection mirror M₁ having a magnification slightly smaller than unity. The reflected light beam is deflected by a planar reflection mirror M₃ which is obliquely disposed at 45° with respect to an optical axis Ax₁ of the first lens group G₁, and then becomes incident on a second lens group G₂ of negative refractive power. The second lens group G₂ comprises, in succession from the incident side of a light beam, a negative lens L₂₁ having a substantially plano-concave shape, a negative meniscus lens L₂₂ having a concave surface facing the incident side, and a positive meniscus lens L₂₃ having a concave surface facing the incident side, and forms a primary image I₁ as a reduced image of an object in the negative lens L₂₁.

The light beam emerging from the second lens group G₂ is reflected by a second concave reflection mirror M₂ having a magnification larger than unity via a fourth lens group G₄ of negative refractive power. The fourth lens group G₄ comprises a negative meniscus lens having a convex surface facing the second concave reflection mirror M₂. The light beam reflected by the second concave reflection mirror M₂ is deflected by a planar reflection mirror M₄, which is obliquely arranged at 45° with respect to an optical axis Ax₂ of the second lens group G₂, via the fourth lens group G₄ again, and becomes incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises, in succession from the incident side of a light beam, a biconvex positive lens L₃₁, a negative meniscus lens L₃₂ having a concave surface facing the incident side, a biconvex positive lens L₃₃, a negative meniscus lens L₃₄ having a concave surface facing the incident side, a positive meniscus lens L₃₅ having a concave surface facing the incident side, a negative meniscus lens L₃₆ having a concave surface facing the incident side, and a positive meniscus lens L₃₇ having a convex surface facing the incident side, and forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁. The negative lens L₂₁ in the second lens group G₂ is arranged at only one side so as not to shield a light beam passing through the first lens group G₁.

The sixth embodiment, as well, has a reduction factor of +0.20 or 1/5 as a whole, and achieves a numerical aperture of (N.A.) of 0.45 in a ring-shaped view field centered at an arc having a radius of 20 mm from the optical axis.

Table 6 below shows data of the sixth embodiment.

In Table 6, the refractive index of each glass material corresponds to that at the wavelength (193 nm) of ArF.

                  TABLE 6                                                          ______________________________________                                         Data of Sixth Embodiment                                                                       Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   169.405   1.0000                                                     Surface)                                                                 1     901.701   30.575    1.560194                                                                               (quartz)                                                                               L.sub.11                             2     -510.578  65.853    1.0000                                               3     220.954   60.000    1.560194                                                                               (quartz)                                                                               L.sub.12                             4     318.898   110.000   1.0000                                               5     295.985   33.350    1.560194                                                                               (quartz)                                                                               L.sub.13                             6     109.856   544.112   1.0000                                               7     -644.876  -578.247  -1.0000         M.sub.1                              8     125.313   -20.000   -1.560194                                                                              (quartz)                                                                               L.sub.21                             9     -19308.942                                                                               -133.068  -1.0000                                              10    285.898   -40.367   -1.560194                                                                              (quartz)                                                                               L.sub.22                             11    239.639   -32.560   -1.0000                                              12    838.750   -48.824   -1.560194                                                                              (quartz)                                                                               L.sub.23                             13    270.000   -413.387  -1.0000                                              14    690.339   -20.000   -1.560194                                                                              (quartz)                                                                               G.sub.4                              15    1371.252  -85.603   -1.0000                                              16    769.864   85.603    1.0000          M.sub.2                              17    1371.252  20.000    1.560194                                                                               (quartz)                                                                               G.sub.4                              18    690.339   478.013   1.0000                                               19    193.080   19.107    1.501375                                                                               (fluorite)                                                                             L.sub.31                             20    -330.493  3.128     1.0000                                               21    237.620   4.8000    1.560194                                                                               (quartz)                                                                               L.sub.32                             22    -404.696  0.100     1.0000                                               23    84.943    25.587    1.501375                                                                               (fluorite)                                                                             L.sub.33                             24    -168.592  0.362     1.0000                                               25    -164.717  13.099    1.560194                                                                               (quartz)                                                                               L.sub.34                             26    -296.532  2.263     1.0000                                               27    -201.221  24.203    1.501375                                                                               (fluorite)                                                                             L.sub.35                             28    -184.897  0.552     1.0000                                               29    -353.513  16.515    1.560194                                                                               (quartz)                                                                               L.sub.36                             30    -514.935  0.691     1.0000                                               31    170.098   29.846    1.560194                                                                               (quartz)                                                                               L.sub.37                             32    642.145   6.065     1.0000                                               33    (Image                                                                         Surface)                                                                         <Condition Corresponding Values>                                               β.sub.M2 = -0.974                                                         β.sub.M1 = -0.762                                                         β.sub.G3 = 0.2013                                                 ______________________________________                                    

FIG. 8 shows coma for explaining the imaging performance of the sixth embodiment. FIG. 8 shows coma in the meridional direction at the center of the ring-shaped view field. Note that a solid curve in FIG. 8 represents coma at 193.3 nm, a broken curve represents coma at 193.3 nm represents coma at 192.9 nm, and a dotted curve represents coma at 193.7 nm. As can be seen from FIG. 8, the sixth embodiment can achieve correction of chromatic aberration within a range of ±0.4 nm at the wavelength of ArF, and maintains an excellent imaging performance.

A seventh embodiment of the present invention will be described below with reference to FIG. 9. Referring to FIG. 9, a light beam from the object surface passes through a first lens group G₁ which comprises a positive meniscus lens L₁₁ having a concave surface facing the incident side of a light beam, a biconvex positive lens L₁₂, and a biconcave negative lens L₁₃, and has positive refractive power as a whole, and becomes incident on a first concave reflection mirror M₁, which has a magnification slightly smaller than unity, via a fifth lens group G₅. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror M₁, and functions to correct aberration generated by the first concave reflection mirror M₁ and second concave reflection mirror M₂. The light beam reflected by the first concave reflection mirror M₁ is deflected by a planar reflection mirror M₃ via the fifth lens group G₅ again, and becomes incident on a second lens group G₂ of positive refractive power.

The planar reflection mirror M₃ is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁ in the light path between the fifth and first lens group G₅ and G₁. The second lens group G₂ comprises a biconvex positive lens L₂₁, a biconcave negative lens L₂₂, and a positive meniscus lens L₂₃ having a concave surface facing the incident side of a light beam. The light beam incident on the second lens group G₂ forms a primary image I₁ as a reduced image of an object in the negative lens L₂₂. The light beam emerging from the second lens group G₂ is deflected by a fourth planar reflection mirror M₄ which is obliquely arranged at 45° with respect to an optical axis Ax₂ of the second lens group G₂, is reflected by the second concave reflection mirror M₂ having a magnification larger than unity, and then becomes incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises a biconvex positive lens L₃₁, a negative meniscus lens L₃₂ having a convex surface facing the incident side, a positive meniscus lens L₃₃ having a convex surface facing the incident side, a biconcave negative lens L₃₄, a biconvex positive lens L₃₅, a positive meniscus lens L₃₆ having a convex surface facing the incident side, and a positive meniscus lens L₃₇ having a convex surface facing the incident side. The third lens group G₃ forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁ at the exit side thereof.

The seventh embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.45 in a ring-shaped view field centered at an arc having a radius of 20 mm from the optical axis.

Table 7 below shows data of the seventh embodiment.

In Table 7, the refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrF.

                  TABLE 7                                                          ______________________________________                                         Data of Seventh Embodiment                                                                     Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   196.209   1.0000                                                     Surface)                                                                 1     -1726.924 54.622    1.508385                                                                               (quartz)                                                                               L.sub.11                             2     260.643   0.100     1.0000                                               3     214.288   55.000    1.508385                                                                               (quartz)                                                                               L.sub.12                             4     -3184.516 61.226    1.0000                                               5     -634.272  15.000    1.508385                                                                               (quartz)                                                                               L.sub.13                             6     142.779   209.364   1.0000                                               7     -324.815  20.000    1.508385                                                                               (quartz)                                                                               G.sub.5                              8     -1599.830 223.380   1.0000                                               9     -537.154  -223.380  -1.0000         M.sub.1                              10    -1599.830 -20.000   -1.508385                                                                              (quartz)                                                                               G.sub.5                              11    -324.815  -355.860  -1.0000                                              12    -286.947  -55.000   -1.508385                                                                              (quartz)                                                                               L.sub.21                             13    1629.963  -101.890  -1.0000                                              14    165.609   -15.000   -1.508385                                                                              (quartz)                                                                               L.sub.22                             15    -750.059  -20.606   -1.0000                                              16    343.901   -39.768   -1.508385                                                                              (quartz)                                                                               L.sub.23                             17    154.033   -630.899  -1.0000                                              18    962.895   630.899   1.0000          M.sub.2                              19    149.915   32.150    1.467877                                                                               (fluorite)                                                                             L.sub.31                             20    -187.485  0.100     1.0000                                               21    -186.839  7.000     1.508385                                                                               (quartz)                                                                               L.sub.32                             22    -727.375  0.100     1.0000                                               23    117.358   20.864    1.508385                                                                               (quartz)                                                                               L.sub.33                             24    647.785   8.591     1.0000                                               25    -284.413  15.450    1.508385                                                                               (quartz)                                                                               L.sub.34                             26    193.285   4.300     1.0000                                               27    388.801   36.187    1.467877                                                                               (fluorite)                                                                             L.sub.35                             28    -216.450  0.100     1.0000                                               29    113.246   19.238    1.467877                                                                               (fluorite)                                                                             L.sub.36                             30    459.066   0.100     1.0000                                               31    221.661   33.854    1.508385                                                                               (quartz)                                                                               L.sub.37                             32    1502.269  15.400    1.0000                                               33    (Image                                                                         Surface)                                                                         <Condition Corresponding Values>                                               β.sub.M2 = -2.008                                                         β.sub.M1 = -1.058                                                         β.sub.G3 = 0.1342                                                 ______________________________________                                    

FIG. 10 shows coma for explaining the imaging performance of the seventh embodiment. FIG. 10 shows coma in the meridional direction at the center of the ring-shaped view field. Note that a solid curve in FIG. 10 represents coma at 248.4 nm, an alternate long and short dashed curve represents coma at 252.4 nm, and an alternate long and two short dashed curve represents coma at 244.4 nm. As can be seen from FIG. 10, the seventh embodiment can achieve correction of chromatic aberration within a range of ±4 nm at the wavelength of KrF, and maintains an excellent imaging performance.

An eighth embodiment of the present invention will be described below with reference to FIG. 11. In the eighth embodiment, as shown in FIG. 11, a light beam from the object surface is incident on a first lens group G₁ of positive refractive power. In the first lens group G₁, the light beam passes through a positive meniscus lens L₁₁ having a concave surface facing the incident side of a light beam, and is then deflected by a planar reflection mirror M₃ which is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁. The deflected light beam passes through a biconvex positive lens L₁₂ and a negative meniscus lens L₁₃ having a convex surface facing the incident side of a light beam, and then reaches a first concave reflection mirror M₁ having a magnification slightly smaller than unity via a fifth lens group G₅ of negative refractive power. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror side. The light beam reflected by the first concave reflection mirror M₁ forms a primary image I₁ as a reduced image of an object via the fifth lens group G₅ again and a second lens group G₂ of positive refractive power.

The second lens group G₂ comprises, in succession from the incident side of a light beam, a biconvex positive lens L₂₁, a negative meniscus lens L₂₂ having a concave surface facing the incident side, and a positive meniscus lens L₂₃ having a concave surface facing the incident side. The light beam from the primary image I₁ is reflected by a second concave reflection mirror M₂ having a magnification larger than unity. The light path of the reflected light beam is deflected by a planar reflection mirror M₄, and the light beam then reaches a third lens group G₃ of positive refractive power. The planar reflection mirror M₄ is obliquely arranged at 45° with respect to an optical axis Ax₃ of the third lens group G₃. The third lens group G₃ comprises, in succession from the incident side of a light beam, a biconvex positive lens L₃₁, a negative meniscus lens L₃₂ having a concave surface facing the incident side, a positive meniscus lens L₃₃ having a convex lens facing the incident side, a biconcave negative lens L₃₄, a positive meniscus lens L₃₅ having a convex surface facing the incident side, a positive meniscus lens L₃₆ having a convex surface facing the incident side, and a positive meniscus lens L₃₇ having a convex surface facing the incident side, and forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁ at its exit side. The positive lens L₁₂ and the negative lens L₁₃ of the first lens group G₁ are arranged at only one side so as to allow a light beam toward the first concave reflection mirror to pass therethrough without shielding a light beam in the second lens group G₂. The second lens group G₂ is arranged at only one side so as to guide a light beam from the first concave reflection mirror M₁ without shielding a light beam in the first lens group G₁.

The eighth embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.30 in a ring-shaped view field centered at an arc having a radius of 20 mm from the optical axis.

Table 8 below shows data of the eighth embodiment.

In Table 8, the refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrF.

                  TABLE 8                                                          ______________________________________                                         Data of Eighth Embodiment                                                                      Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   196.018   1.0000                                                     Surface)                                                                 1     -5157.341 35.000    1.508385                                                                               (quartz)                                                                               L.sub.11                             2     -342.424  264.350   1.0000                                               3     418.888   35.000    1.508385                                                                               (quartz)                                                                               L.sub.12                             4     -2971.961 0.100     1.0000                                               5     479.951   35.000    1.508385                                                                               (quartz)                                                                               L.sub.13                             6     219.080   314.800   1.0000                                               7     -194.621  18.000    1.508385                                                                               (quartz)                                                                               G.sub.5                              8     -370.491  159.400   1.0000                                               9     -586.251  -159.400  -1.0000         M.sub.1                              10    -370.491  -18.000   -1.508385                                                                              (quartz)                                                                               G.sub.5                              11    -194.621  -187.600  -1.0000                                              12    -275.679  35.500    -1.508385                                                                              (quartz)                                                                               L.sub.21                             13    507.601   -112.350  -1.0000                                              14    144.909   -6.500    -1.508385                                                                              (quartz)                                                                               L.sub.22                             15    -700.764  -35.700   -1.0000                                              16    198.506   -35.000   -1.508385                                                                              (quartz)                                                                               L.sub.23                             17    137.057   -793.600  -1.0000                                              18    934.699   697.100   1.0000          M.sub.2                              19    167.048   23.800    1.467877                                                                               (fluorite)                                                                             L.sub.31                             20    -305.250  3.250     1.0000                                               21    -269.515  6.500     1.508385                                                                               (quartz)                                                                               L.sub.32                             22    1602.279  0.100     1.0000                                               23    83.085    35.000    1.467871                                                                               (fluorite)                                                                             L.sub.33                             24    534.963   8.000     1.0000                                               25    -2442.622 28.500    1.508385                                                                               (quartz)                                                                               L.sub.34                             26    51.803    1.350     1.0000                                               27    52.498    23.600    1.467877                                                                               (fluorite)                                                                             L.sub.35                             28    895.515   0.100     1.0000                                               29    159.859   23.400    1.467877                                                                               (fluorite)                                                                             L.sub.36                             30    1657.174  0.100     1.0000                                               31    216.018   7.500     1.508385                                                                               (quartz)                                                                               L.sub.37                             32    434.319   15.000    1.0000                                               33    (Image                                                                         Surface)                                                                 <Condition Corresponding Values>                                               β.sub.M2 = -1.684                                                         β.sub.M1 = -0.8795                                                        β.sub.G3 = 0.2035                                                         ______________________________________                                    

FIG. 12 shows coma for explaining the imaging performance of the eighth embodiment. FIG. 12 shows coma in the meridional direction at the center of the ring-shaped view field. Note that a solid curve in FIG. 12 represents coma at 248.4 nm, a broken curve represents coma at 238.4 nm, and a dotted curve represents coma at 258.4 nm. As can be seen from FIG. 12, the eighth embodiment can achieve correction of chromatic aberration within a range of ±10 nm at the wavelength of KrF, and maintains an excellent imaging performance.

A ninth embodiment of the present invention will be described below with reference to FIG. 13. In the ninth embodiment shown in FIG. 13, a second concave reflection mirror M₂ comprises a reflection mirror having a non-spherical surface. Referring to FIG. 13, a light beam from the object surface reaches a first concave reflection mirror M₁ having a magnification slightly smaller than unity via a first lens group G₁ which comprises a positive meniscus lens L₁₁ having a concave surface facing the incident side of a light beam, a positive meniscus lens L₁₂ having a convex surface facing the incident side, a positive meniscus lens L₁₃ having a convex surface facing the incident side, and a positive meniscus lens L₁₄ having a convex surface facing the incident side, and has positive refractive power as a whole, and a fifth lens group G₅ of negative refractive power. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror side. The light beam reflected by the first concave reflection mirror M₁ is deflected by a planar reflection mirror M₃, which is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁, via the fifth lens group G₅ again, and then becomes incident on a second lens group G₂ of negative refractive power. The second lens group G₂ comprises a biconvex positive lens L₂₁, a biconcave negative lens L₂₂, and a positive meniscus lens L₂₃ having a convex surface facing the incident side of a light beam, and forms a primary reduced image I₁ at its exit side.

The light beam from the primary image I₁ is deflected by a planar reflection mirror M₄ which is obliquely arranged at 45° with respect to an optical axis Ax₂ of the second lens group G₂, and reaches a second concave reflection mirror M₂ having a magnification larger than unity and a non-spherical shape. The light beam reflected by the second concave reflection mirror M₂ becomes incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises a biconvex positive lens L₃₁, a biconcave negative lens L₃₂, a biconvex positive lens L₃₃, a positive meniscus lens L₃₄ having a convex surface facing the incident side of a light beam, a positive meniscus lens L₃₅ having a convex surface facing the incident side, a negative meniscus lens L₃₆ having a convex surface facing the incident side, and a positive meniscus lens L₃₇ having a convex surface facing the incident side, and forms a-secondary image I₂ in a larger reduction scale than that of the primary image I₁. The ninth embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.5 in a ring-shaped view field centered at an arc having a radius of 24.25 mm from the optical axis.

Table 9 below shows data of the ninth embodiment.

In Table 9, as for the non-spherical reflection surface, only the radius of paraxial curvature is presented, and when a tangential plane at the vertex of a non-spherical surface is considered, a position, where the optical axis passes, on the tangential plane is defined as an origin, and a displacement, in the optical axis direction, of the non-spherical surface at a position of a height y on the tangential plane is represented by x with reference to the vertex of the non-spherical surface while the propagating direction of light is assumed to be the positive direction, the non-spherical surface shape is given by the following equation:

    x=cy.sup.2 /{1+(1-κc.sup.2 y.sup.2).sup.1/2 }+C.sub.4 y.sup.4 +C.sub.6 y.sup.6 +C.sub.8 y.sup.8 +C.sub.10 y.sup.10

where c is the curvature (the reciprocal number of the radius r of curvature) of the non-spherical surface at the vertex of the non-spherical surface, κ is a quadrics parameter, and C₄, C₆, C₈, and C₁₀ are non-spherical surface coefficients.

In Table 9, the refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrF.

                  TABLE 9                                                          ______________________________________                                         Ninth Embodiment                                                                               Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   537.071   1.0000                                                     Surface)                                                                 1     -13337.695                                                                               38.029    1.508385                                                                               (quartz)                                                                               L.sub.11                             2     -559.442  0.100     1.0000                                               3     329.313   71.406    1.508385                                                                               (quartz)                                                                               L.sub.12                             4     4423.247  0.100     1.0000                                               5     208.809   57.000    1.508385                                                                               (quartz)                                                                               L.sub.13                             6     247.488   54.831    1.0000                                               7     889.869   50.000    1.508385                                                                               (quartz)                                                                               L.sub.14                             8     140.636   362.130   1.0000                                               9     -277.199  15.000    1.508385                                                                               (quartz)                                                                               G.sub.5                              10    -485.421  540.415   1.0000                                               11    -1017.359 -540.415  -1.0000         M.sub.1                              12    -485.421  -15.000   -1.508385                                                                              (quartz)                                                                               G.sub.5                              13    -277.199  -326.174  -1.0000                                              14    -494.427  -48.250   -1.508385                                                                              (quartz)                                                                               L.sub.21                             15    491.077   -38.033   -1.0000                                              16    361.893   -10.000   -1.508385                                                                              (quartz)                                                                               L.sub.22                             17    -260.009  -40.978   -1.0000                                              18    -279.421  -17.860   -1.508385                                                                              (quartz)                                                                               L.sub.23                             19    -543.231  -934.426  -1.0000                                              20    1153.584  773.262   1.0000  (non-   M.sub.2                                                                spherical)                                   21    187.601   29.381    1.467877                                                                               (fluorite)                                                                             L.sub.31                             22    -1450.353 6.033     1.0000                                               23    -391.392  9.000     1.508385                                                                               (quartz)                                                                               L.sub.32                             24    179.475   3.183     1.0000                                               25    213.669   29.199    1.467877                                                                               (fluorite)                                                                             L.sub.33                             26    -621.952  0.100     1.0000                                               27    137.369   29.803    1.508385                                                                               (quartz)                                                                               L.sub.34                             28    458.595   0.100     1.0000                                               29    135.180   28.421    1.467877                                                                               (fluorite)                                                                             L.sub.35                             30    268.007   0.100     1.0000                                               31    121.989   16.840    1.508385                                                                               (quartz)                                                                               L.sub.36                             32    87.217    11.990    1.0000                                               33    111.525   42.765    1.467877                                                                               (fluorite)                                                                             L.sub.37                             34    841.067   19.747    1.0000                                               35    (Image                                                                         Surface)                                                                 <Non-spherical Surface Coefficient>                                            21st surface (second concave reflection mirror M.sub.2)                        κ  1.0                                                                   C.sub.4  0.980896 × 10.sup.-10                                           C.sub.6  0.374676 × 10.sup.-15                                           C.sub.8  0.830862 × 10.sup.-21                                           C.sub.10 0.705084 × 10.sup.-26                                           <Condition Corresponding Values>                                               β.sub.M2 = -1.733                                                         β.sub.M1 = -0.811                                                         β.sub.G3 = 0.157                                                          ______________________________________                                    

FIG. 14 shows coma of the ninth embodiment. FIG. 14 shows coma in the meridional direction at the center of the ring-shaped view field. As can be seen from FIG. 14, the ninth embodiment maintains an excellent imaging performance.

A 10th embodiment of the present invention will be described below with reference to FIG. 15. In the 10th embodiment, each of first and second concave reflection mirrors M₁ and M₂ has a non-spherical reflection surface. Referring to FIG. 15, a light beam from the object surface passes through a first lens group G₁ which comprises a biconvex positive lens L₁₁, a positive meniscus lens L₁₂ having a convex surface facing the incident side of a light beam, a negative meniscus lens L₁₃ having a convex surface facing the incident side, and a negative meniscus lens L₁₄ having a convex surface facing the incident side, and has positive refractive power as a whole, and then reaches a first concave reflection mirror M₁ having a magnification slightly Smaller than unity via a fifth lens group G₅ of negative refractive power. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror M₁ side.

The light beam reflected by the first concave reflection mirror M₁ is deflected by a planar reflection mirror M₃, which is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁, via the fifth lens group G₅ again, and becomes incident on a second lens group G₂ of negative refractive power. The second lens group G₂ comprises a negative meniscus lens L₂₁ having a convex surface facing the incident side of a light beam, a biconcave negative lens L₂₂, and a biconvex positive lens L₂₃, and forms a primary image I₁ as a reduced image of an object between the negative lens L₂₂ and the positive lens L₂₃. The light beam emerging from the second lens group G₂ is deflected by a planar reflection mirror M₄, which is obliquely arranged at 45° with respect to an optical axis Ax₂ of the second lens group G₂, and reaches a second concave reflection mirror M₂ having a magnification larger than unity. The light beam reflected by the second concave reflection mirror M₂ is incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises, in succession from the incident side of a light beam, a negative meniscus lens L₃₁ having a convex surface facing the object side, a biconvex positive lens L₃₂, a positive meniscus lens L₃₃ having a convex surface facing the incident side, a negative meniscus lens L₃₄ having a concave surface facing the incident side, and a biconvex positive lens L₃₅, and forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁ at the exit side of the third lens group G₃.

The 10th embodiment, as well, has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.45 in a ring-shaped view field centered at an arc having a radius of 24.25 mm from the optical axis.

Table 10 below shows data of the 10th embodiment.

Note that the radius of curvature of each of the first and second concave reflection mirrors M₁ and M₂ shown in Table 10 is the radius of paraxial curvature, and the non-spherical surface coefficients of these first and second reflection mirrors M₁ and M₂ are separately listed. The refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrP.

                  TABLE 10                                                         ______________________________________                                         10th Embodiment                                                                                Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   414.498   1.0000                                                     Surface)                                                                 1     8211.322  38.636    1.508385                                                                               (quartz)                                                                               L.sub.11                             2     -439.506  0.100     1.0000                                               3     239.531   74.172    1.508385                                                                               (quartz)                                                                               L.sub.12                             4     1059.356  0.100     1.0000                                               5     220.874   71.349    1.508385                                                                               (quartz)                                                                               L.sub.13                             6     192.087   28.244    1.0000                                               7     9114.936  13.285    1.508385                                                                               (quartz)                                                                               L.sub.14                             8     135.907   347.569   1.0000                                               9     -236.652  19.683    1.508385                                                                               (quartz)                                                                               G.sub.5                              10    -287.731  551.277   1.0000                                               11    -1024.933 -551.277  -1.0000 (non-   M.sub.1                                                                spherical)                                   12    -287.731  -19.683   -1.508385                                                                              (quartz)                                                                               G.sub.5                              13    -236.652  -314.837  -1.0000                                              14    -149.845  -31.308   -1.508385                                                                              (quartz)                                                                               L.sub.21                             15    -137.269  -33.137   -1.0000                                              16    257.207   -10.000   -1.508385                                                                              (quartz)                                                                               L.sub.22                             17    -315.674  -37.792   -1.0000                                              18    -459.634  -27.954   -1.508385                                                                              (quartz)                                                                               L.sub.23                             19    431.125   -848.560  -1.0000                                              20    1044.120  752.496   1.0000  (non-   M.sub.2                                                                spherical)                                   21    106.792   12.000    1.508385                                                                               (quartz)                                                                               L.sub.31                             22    105.550   24.044    1.0000                                               23    344.933   16.641    1.508385                                                                               (quartz)                                                                               L.sub.32                             24    -1397.225 0.100     1.0000                                               25    105.435   30.284    1.508385                                                                               (quartz)                                                                               L.sub.33                             26    890.603   8.066     1.0000                                               27    -297.345  32.551    1.508385                                                                               (quartz)                                                                               L.sub.34                             28    -486.516  1.643     1.0000                                               29    154.666   44.945    1.508385                                                                               (quartz)                                                                               L.sub.35                             30    -706.316  24.770    1.0000                                               31    (Image                                                                         Surface)                                                                 <Non-spherical Surface Coefficient>                                            11th surface (first concave reflection mirror M.sub.1)                         κ  1.0                                                                   C.sub.4  -0.395493 × 10.sup.-12                                          C.sub.6  -0.168923 × 10.sup.-16                                          C.sub.8  -0.338178 × 10.sup.-22                                          C.sub.10 -0.134005 × 10.sup.-26                                          20th surface (second concave reflection mirror M.sub.2)                        κ  1.0                                                                   C.sub.4  0.340990 × 10.sup.-10                                           C.sub.6  0.116056 × 10.sup.-15                                           C.sub.8  0.245212 × 10.sup.-21                                           C.sub.10 0.260273 × 10.sup.-26                                           <Condition Corresponding Values>                                               β.sub.M2 = -1.357                                                         β.sub.M1 = -0.800                                                         β.sub.G3 = 0.238                                                          ______________________________________                                    

FIG. 16 shows coma of the 10th embodiment. FIG. 16 shows coma in the meridional direction at the center of the ring-shaped view field. As can be seen from FIG. 16, the 10th embodiment maintains an excellent imaging performance.

An 11th embodiment of the present invention will be described below with reference to FIG. 17. Referring to FIG. 17, a light beam from the object surface emerges from a first lens group G₁ which comprises a biconvex positive lens L₁₁, a positive meniscus lens L₁₂ having a convex surface facing the incident side of a light beam, a positive meniscus lens L₁₃ having a convex surface facing the incident side of a light beam, and a negative meniscus lens L₁₄ having a convex surface facing the incident side, and has positive refractive power as a whole, and is deflected by a planar reflection mirror M₃ which is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁. The deflected light beam reaches a first concave reflection mirror M₁ having a magnification slightly smaller than unity via a fifth lens group G₅ of negative refractive power. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror M₁. The light beam reflected by the first concave reflection mirror M₁ is incident on a second lens group G₂ of negative refractive power via the second lens group G₅ again. The second lens group G₂ comprises a negative meniscus lens L₂₁ having a convex surface facing the incident side of a light beam, a biconcave negative lens L₂₂, a positive meniscus lens L₂₃ having a concave surface facing the incident side, and a positive meniscus lens L₂₄ having a concave surface facing the incident side, and forms a primary image I₁ as a reduced image of an object in the light path between the negative lenses L₂₁ and L₂₂. Note that the negative lens L₂₁ in the second lens group is arranged at only one side of the optical axis Ax₂ so as not to shield the light path extending from the first lens group G₁ toward the first concave reflection mirror M₁.

The light beam emerging from the second lens group G₂ is deflected by a planar reflection mirror M₄ which is obliquely arranged at 45° with respect to the optical axis Ax₂ of the second lens group G₂, is reflected by a second concave reflection mirror M₂ having a magnification larger than unity, and then becomes incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises a negative meniscus lens L₃₁ having a convex surface facing the incident side of a light beam, a biconvex positive lens L₃₂, a positive meniscus lens L₃₃ having a convex surface facing the incident side, a biconcave negative lens L₃₄, and a biconvex positive lens L₃₅, and forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁.

The 11th embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.4 in a ring-shaped view field centered at an arc having a radius of 25 mm from the optical axis.

Table 11 below shows data of the 11th embodiment.

In Table 11, the refractive index of each glass material corresponds to that at the wavelength (193 nm) of ArF.

                  TABLE 11                                                         ______________________________________                                         11th Embodiment                                                                                Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   298.019   1.0000                                                     Surface)                                                                 1     4860.661  33.000    1.501375                                                                               (fluorite)                                                                             L.sub.11                             2     -410.727  0.100     1.0000                                               3     202.797   73.000    1.501375                                                                               (fluorite)                                                                             L.sub.12                             4     221.645   12.851    1.0000                                               5     189.285   33.370    1.501375                                                                               (fluorite)                                                                             L.sub.13                             6     308.080   19.873    1.0000                                               7     942.449   50.409    1.560194                                                                               (quartz)                                                                               L.sub.14                             8     133.378   326.305   1.0000                                               9     -409.199  21.087    1.501375                                                                               (fluorite)                                                                             G.sub.5                              10    -618.117  538.975   1.0000                                               11    -918.138  -538.975  -1.0000         M.sub.1                              12    -618.117  -21.087   -1.501375                                                                              (fluorite)                                                                             G.sub.5                              13    -409.199  -230.534  -1.0000                                              14    -124.583  -16.666   -1.501375                                                                              (fluorite)                                                                             L.sub.21                             15    -122.761  -99.533   -1.0000                                              16    139.122   -17.104   -1.501375                                                                              (fluorite)                                                                             L.sub.22                             17    -708.717  -35.132   -1.0000                                              18    253.980   -28.131   -1.501375                                                                              (fluorite)                                                                             L.sub.23                             19    225.928   -6.072    -1.0000                                              20    14003.190 -33.317   -1.560194                                                                              (quartz)                                                                               L.sub.24                             21    290.144   -904.186  -1.0000                                              22    1085.235  804.185   1.0000          M.sub.2                              23    95.505    18.738    1.560194                                                                               (quartz)                                                                               L.sub.31                             24    92.560    23.254    1.0000                                               25    1178.101  22.112    1.501375                                                                               (fluorite)                                                                             L.sub.32                             26    -788.023  0.100     1.0000                                               27    86.141    27.769    1.501375                                                                               (fluorite)                                                                             L.sub.33                             28    734.979   1.972     1.0000                                               29    -322.980  43.543    1.560194                                                                               (quartz)                                                                               L.sub.34                             30    926.558   0.100     1.0000                                               31    125.704   23.783    1.501375                                                                               (fluorite)                                                                             L.sub.35                             32    -725.241  15.000    1.0000                                               33    (Image                                                                         Surface)                                                                 <Condition Corresponding Values>                                               β.sub.M2 = -0.993                                                         β.sub.M1 = -0.814                                                         β.sub.G3 = 0.373                                                          ______________________________________                                    

FIG. 18 shows coma of the 11th embodiment. FIG. 18 shows coma in the meridional direction at the center of the ring-shaped view field. Note that a solid curve in FIG. 18 represents coma at 193.3 nm, a broken curve represents coma at 193.7 nm, and a dotted curve represents coma at 192.9 nm. As can be seen from FIG. 18, the 11th embodiment can achieve correction of chromatic aberration within a range of ±0.4 nm at the wavelength of ArF, and maintains art excellent imaging performance.

A 12th embodiment of the present invention will be described below with reference to FIG. 19. Referring to FIG. 19, a light beam from the object surface passes through a first lens group G₁ which comprises a biconvex positive lens L₁₁, a biconvex positive lens L₁₂, a negative meniscus lens L₁₃ having a convex surface facing the incident side of a light beam, and a biconcave negative lens L₁₄, and which has positive refractive power as a whole, and is then deflected by a planar reflection mirror M₃ which is obliquely arranged at 45° with respect to an optical axis Ax₁ of the first lens group G₁. The deflected light beam reaches a first concave reflection mirror M₁ having a magnification slightly smaller than unity via a fifth lens group G₅ of negative refractive power. The fifth lens group G₅ comprises a negative meniscus lens having a convex surface facing the first concave reflection mirror M₁ side. The light beam reflected by the first concave reflection mirror M₁ is incident on a second lens group G₂ of negative refractive power via the fifth lens group G₅ again. The second lens group G₂ comprises a negative meniscus lens L₂₁ having a convex surface facing the incident side of a light beam, a negative meniscus lens L₂₂ having a concave surface facing the incident side, a negative meniscus lens L₂₃ having a concave surface facing the incident side, and a biconvex positive lens L₂₄, and forms a primary reduced image I₁ between the negative lenses L₂₁ and L₂₂.

The light beam emerging from the second lens group G₂ is deflected by a planar reflection mirror M₄ which is obliquely arranged at 45° with respect to an optical axis Ax₂ of the second lens group G₂, is reflected by a second concave reflection mirror M₂ having a magnification larger than unity, and then becomes incident on a third lens group G₃ of positive refractive power. The third lens group G₃ comprises a negative meniscus lens L₃₁ having a convex surface facing the incident side of a light beam, a biconvex positive lens L₃₂, a biconvex positive lens L₃₃, a negative meniscus lens L₃₄ having a concave surface facing the incident side, and a positive meniscus lens L₃₅ having a convex surface facing the incident side, and forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁ at its exit side.

The 12th embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture of (N.A.) of 0.4 in a ring-shaped view field entered at an arc having a radius of 24.25 mm from the optical axis.

Table 12 below shows data of the 12th embodiment.

In Table 12, the refractive index of each glass material corresponds to that at the wavelength (248 nm) of KrF.

                  TABLE 12                                                         ______________________________________                                         12th Embodiment                                                                                Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   400.975   1.0000                                                     Surface)                                                                 1     3191.354  33.000    1.508385                                                                               (quartz)                                                                               L.sub.11                             2     -448.984  15.428    1.0000                                               3     223.181   64.645    1.508385                                                                               (quartz)                                                                               L.sub.12                             4     -4151.509 12.219    1.0000                                               5     11253.765 49.299    1.508385                                                                               (quartz)                                                                               L.sub.13                             6     461.799   16.133    1.0000                                               7     -1336.016 48.239    1.508385                                                                               (quartz)                                                                               L.sub.14                             8     158.062   281.551   1.0000                                               9     -312.940  20.065    1.508385                                                                               (quartz)                                                                               G.sub.5                              10    -441.735  538.318   1.0000                                               11    -919.752  -538.318  -1.0000         M.sub.1                              12    -441.735  -20.065   -1.508385                                                                              (quartz)                                                                               G.sub.5                              13    -312.940  -247.755  -1.0000                                              14    -132.399  -22.942   -1.508385                                                                              (quartz)                                                                               L.sub.21                             15    -127.754  -104.702  -1.0000                                              16    134.695   -14.420   -1.508385                                                                              (quartz)                                                                               L.sub.22                             17    11180.397 -23.490   -1.0000                                              18    160.735   -29.211   -1.508385                                                                              (quartz)                                                                               L.sub.23                             19    163.686   -0.100    -1.0000                                              20    1939.060  -37.447   -1.508385                                                                              (quartz)                                                                               L.sub.24                             21    239.738   -905.619  -1.0000                                              22    1073.545  806.574   1.0000          M.sub.2                              23    89.424    16.314    1.508385                                                                               (quartz)                                                                               L.sub.31                             24    82.394    13.739    1.0000                                               25    612.232   15.000    1.508385                                                                               (quartz)                                                                               L.sub.32                             26    -1320.781 0.100     1.0000                                               27    86.666    25.509    1.508385                                                                               (quartz)                                                                               L.sub.33                             28    -1224.142 4.770     1.0000                                               29    -224.139  36.310    1.508385                                                                               (quartz)                                                                               L.sub.34                             30    -236.345  0.589     1.0000                                               31    165.225   24.171    1.508385                                                                               (quartz)                                                                               L.sub.35                             32    43423.922 15.000    1.0000                                               33    (Image                                                                         Surface)                                                                 <Condition Corresponding Values>                                               β.sub.M2 = -0.934                                                         β.sub.M1 = -0.797                                                         β.sub.G3 = 0.400                                                          ______________________________________                                    

FIG. 20 shows coma of the 12th embodiment. FIG. 20 shows coma in the meridional direction at the center of the ring-shaped view field. As can be seen from FIG. 20, the 12th embodiment maintains an excellent imaging performance.

In each of the above embodiments, the primary image formed by the first partial optical system (the first lens group G₁ and the first concave reflection mirror M₁) is a reduced image. However, the primary image formed by the first partial optical system is not limited to a reduced image.

In each of the above embodiments, since the optical system is constituted to satisfy the above-mentioned conditions, the optical members constituting the catadioptric reduction projection optical system do not interfere with each other. Therefore, a physically constructible catadioptric reduction projection optical system can be obtained.

In each of the fifth to 12th embodiments, the optical system is preferably constituted to satisfy:

    -2.0<β.sub.M1 <-0.7

where B_(M1) is the magnification of the first concave reflection mirror M₁.

In each of the sixth to 12th embodiments, the object surface is set to be parallel to the image surface using the two planar reflection mirrors. Thus, when the catadioptric reduction projection optical system of each of the second to 12th embodiments is adopted as an optical system of a scanning exposure apparatus, a convey mechanism for executing scanning exposure can be simplified.

In each of the second, third, fourth, and seventh embodiments, since the lens groups of the catadioptric reduction projection optical system are constituted by two different optical members, chromatic aberration is corrected.

Still other preferred embodiments of the present invention will be described below. FIG. 21 shows a light path of a 13th embodiment of the present invention. As shown in FIG. 21, a light beam from the object surface passes through a first lens group G₁ of positive refractive power, and its light path is bent by a planar reflection mirror M₃. The light beam passes through a second lens group G₂ and is reflected by a first concave reflection mirror M₁ having a magnification slightly smaller than unity magnification.

The first lens group G₁ comprises a plano-convex positive lens L₁₁ having a planar surface facing the object surface, a positive meniscus lens L₁₂ having a convex surface facing the object side, a negative meniscus lens L₁₃ having a convex surface facing the object side, and a positive meniscus lens L₁₄ having a concave surface facing the incident side. The planar reflection mirror M₃ is disposed between the positive meniscus lens L₁₂ and the negative meniscus lens L₁₃.

The second lens group G₂ is disposed between the first lens group G₁ and the first concave reflection mirror M₁, and comprises a negative meniscus lens L₂₁ having a convex surface facing the first concave reflection mirror M₁ side.

The first lens group G₁ mainly functions to correct distortion and to maintain telecentric characteristics. The second lens group G₂ mainly functions to correct coma of high orders generated by the first and second concave reflection mirrors M₁ and M₂.

The light beam reflected by the first concave reflection mirror M₁ passes through the second lens group G₂ to form a primary reduced image I₁ between a negative meniscus lens L₃₂ and a positive meniscus lens L₃₃. A third lens group G₃ comprises a positive meniscus lens L₃₁ having a convex surface facing the first concave reflection mirror M₁ side, the negative almost plano-concave lens L₃₂ having a concave surface facing the primary image I₁ side, and the positive meniscus lens L₃₃ of weak refractive power having a concave surface facing the primary image I₁ side. The third lens group G₃ functions to correct distortion and curvature of field, and functions as a field lens.

After the light path of the light beam is bent by a planar reflection mirror M₄, the light beam emerging from the third lens group G₃ is reflected by the second concave reflection mirror M₂. The light beam reflected by the second concave reflection mirror M₂ is incident on a fourth lens group G₄ of positive refractive power. The fourth lens group G₄ comprises, in succession from the incident side of a light beam, positive meniscus lenses L₄₁ and L₄₂ each having a convex surface facing the second concave reflection mirror M₂ side, a biconvex lens L₄₃, a biconcave lens L₄₄, a biconvex lens L₄₅, a negative meniscus lens L₄₆ having a convex surface facing the second concave reflection mirror M₂ side, and a positive meniscus lens L₄₇ having a convex surface facing the second concave reflection mirror M₂ side. The fourth lens group G₄ forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁.

At this time, only part of each of the negative meniscus lens L₁₃ and the positive meniscus lens L₁₄ in the first lens group G₁ and the positive meniscus lens L₃₁ and the negative meniscus lens L₃₂ in the third lens group G₃ is used so as not to shield opposing light paths. Like the negative meniscus lens L₁₃, the positive meniscus lens L₁₄, the positive meniscus lens L₃₁, and the negative meniscus lens L₃₂, part of the positive meniscus lens L₃₃ in the third lens group is used so as not to shield a light beam bent by the planar reflection mirror M₄.

The 13th embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture (N.A.) of 0.45 in a ring-shaped view field centered on a wafer having a radius of 20 mm from the optical axis. The center and spread of wavelengths of a light source used for illumination are λ=217±4 nm.

Data of the 13th embodiment are shown in Table 13 below.

In Table 13, signs of the refractive index and the plane-to-plane distance are inverted by the reflection by the concave reflection mirror. The refractive index of each glass material corresponds to that at the center wavelength (217 nm). The positions of the planar reflection mirrors M₃ and M₄ for bending an optical path are omitted since they are not essential in the optical design.

                  TABLE 13                                                         ______________________________________                                         Data of 13th Embodiment                                                                        Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   195.426   1.0000                                                     Surface)                                                                 1     ∞   28.240    1.53126 (quartz)                                                                               L.sub.11                             2     -357.547  0.100     1.0000                                               3     230.557   40.000    1.53126 (quartz)                                                                               L.sub.12                             4     511.280   127.690   1.0000                                               5     878.395   15.000    1.53126 (quartz)                                                                               L.sub.13                             6     147.119   30.000    1.0000                                               7     -460.235  21.395    1.53126 (quartz)                                                                               L.sub.14                             8     -331.076  503.034   1.0000                                               9     -249.818  20.000    1.53126 (quartz)                                                                               L.sub.21                             10    -339.471  197.664   1.0000                                               11    -788.338  -197.664  -1.0000         M.sub.1                              12    -339.471  -20.000   -1.53126                                                                               (quartz)                                                                               L.sub.21                             13    -249.818  -476.065  -1.0000                                              14    -190.475  -35.000   -1.53126                                                                               (quartz)                                                                               L.sub.31                             15    -519.430  -34.164   -1.0000                                              16    -5178.591 -15.000   -1.48295                                                                               (fluorite)                                                                             L.sub.32                             17    -168.466  -237.584  -1.0000                                              18    210.704   -9.790    -1.53126                                                                               (quartz)                                                                               L.sub.33                             19    200.000   -800.100  -1.0000                                              20    1107.209  800.100   1.0000          M.sub.2                              21    198.147   14.809    1.48295 (fluorite)                                                                             L.sub.41                             22    372.888   0.100     1.0000                                               23    129.330   25.653    1.53126 (quartz)                                                                               L.sub.42                             24    557.405   0.100     1.0000                                               25    444.552   14.301    1.48295 (fluorite)                                                                             L.sub.43                             26    -3249.866 7.298     1.0000                                               27    -295.228  8.000     1.53126 (quartz)                                                                               L.sub.44                             28    206.396   0.100     1.0000                                               29    206.202   25.530    1.48295 (fluorite)                                                                             L.sub.45                             30    -284.380  0.100     1.0000                                               31    141.752   45.000    1.53126 (quartz)                                                                               L.sub.46                             32    72.518    1.447     1.0000                                               33    80.818    40.000    1.53126 (quartz)                                                                               L.sub.47                             34    -1726.119 15.000    1.0000                                               <Condition Corresponding Values>                                               β.sub.M1 = -0.959                                                         β.sub.M2 = -1.646                                                         β.sub.G4 = 0.178                                                          ______________________________________                                    

FIG. 22 shows coma for explaining the imaging performance of the 13th embodiment. FIG. 22 shows coma in the meridional and sagittal directions at the center of the ring-shaped view field. A broken curve represents coma at 213 nm, a solid curve represents come at 217 nm, and a dotted curve represents coma at 221 nm. As can be seen from FIG. 22, the catadioptric reduction projection optical system of the 13th embodiment performs correction of aberration within this range, and has an excellent imaging performance.

The 14th embodiment will be described below with reference to FIG. 23. As shown in FIG. 23, a light beam from the object surface passes through a first lens group G₁ of positive refractive power, and its light path is bent by a planar reflection mirror M₃. The light beam passes through a second lens group G₂ and is reflected by a first concave reflection mirror M₁ having a magnification slightly smaller than unity magnification. The first lens group G₁ comprises a plano-convex positive lens L₁₁ having its planar surface facing the object surface, a positive biconvex lens L₁₂, and a negative biconcave lens L₁₃. The second lens group G₂ is disposed between the first lens group G₁ and the first concave reflection mirror M₁, and comprises a positive plano-convex lens L₂₁ having a convex surface facing the planar reflection mirror M₃ side, and a negative meniscus lens L₂₂ having a convex surface facing the first concave reflection mirror M₁ side.

The first lens group G₁ mainly functions to correct distortion and to maintain telecentric characteristics. The second lens group G₂ mainly functions to correct coma of high orders generated by the first and second concave reflection mirrors M₁ and M₂.

The light beam reflected by the first concave reflection mirror M₁ passes through the third lens group G₃ via the second lens group G₂ to form a primary reduced image I₁. The third lens group G₃ comprises a positive meniscus lens L₃₁ having a convex surface facing the first concave reflection mirror side, a negative meniscus lens L₃₂ having a concave surface facing the primary image I₁ side, and a biconvex lens L₃₃. The third lens group G₃ functions to correct distortion and curvature of field, and functions as a field lens.

After the light path of the light beam is bent by a planar reflection mirror M₄, the light beam emerging from the third lens group G₃ is reflected by the second concave reflection mirror M₂ and is incident on a fourth lens group G₄ of positive refractive power. The fourth lens group G₄ comprises, in succession from the incident side of a light beam, a positive meniscus lens L₄₁ having a convex lens facing the second concave reflection mirror M₂ side, a negative meniscus lens L₄₂ having a concave surface facing the second concave reflection mirror M₂ side, a biconvex lens L₄₃, a biconcave lens L₄₄, a positive meniscus lens L₄₅ having a convex surface facing the second concave reflection mirror M₂ side, a negative meniscus lens L₄₆ having a convex surface facing the second concave reflection mirror M₂ side, and a positive meniscus lens L₄₇ having a convex surface facing the second concave reflection mirror M₂ side. The fourth lens group G₄ forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁.

At this time, only part of each of the biconcave lens L₁₃ in the first lens group G₁ and the planar reflection mirror M₃ is used so as not to shield opposing light paths.

The 14th embodiment has a reduction factor of +0.25 or 1/4 as a whole, and achieves a numerical aperture (N.A.) of 0.45 in a ring-shaped view field centered on a wafer having a radius of 20 mm from the optical axis. The center and spread of wavelengths of a light source used for illumination are λ=217±4 nm.

Data of the 14th embodiment are shown in Table 14 below.

In Table 14, signs of the refractive index and the plane-to-plane distance are inverted by the reflection by the concave reflection mirror. The refractive index of each glass material corresponds to that at the center wavelength (217 nm). The positions of the planar reflection mirrors M₃ and M₄ for bending an optical path are omitted since they are not essential in the optical design.

                  TABLE 14                                                         ______________________________________                                         Data of 14th Embodiment                                                                        Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   326.189   1.0000                                                     Surface)                                                                 1     ∞   40.000    1.53126 (quartz)                                                                               L.sub.11                             2     -509.905  0.500     1.0000                                               3     290.348   57.790    1.53126 (quartz)                                                                               L.sub.12                             4     -302.026  1.115     1.0000                                               5     -297.387  15.000    1.53126 (quartz)                                                                               L.sub.13                             6     291.877   584.373   1.0000                                               7     900.000   30.000    1.53126 (quartz)                                                                               L.sub.21                             8     ∞   50.000    1.0000                                               9     -225.015  20.000    1.53126 (quartz)                                                                               L.sub.22                             10    -550.380  155.364   1.0000                                               11    -714.562  -155.364  -1.0000         M.sub.1                              12    -550.380  -20.000   -1.53126                                                                               (quartz)                                                                               L.sub.22                             13    -225.015  -50.000   -1.0000                                              14    ∞   -30.000   -1.53126                                                                               (quartz)                                                                               L.sub.21                             15    900.000   -481.784  -1.0000                                              16    -257.121  -35.000   -1.48295                                                                               (quartz)                                                                               L.sub.31                             17    -306.348  -34.164   -1.0000                                              18    -238.821  -15.000   -1.53126                                                                               (quartz)                                                                               L.sub.32                             19    -202.203  -24.613   -1.0000                                              20    -94514.655                                                                               -14.817   -1.53126                                                                               (quartz)                                                                               L.sub.33                             21    1000.000  -965.156  -1.0000                                              22    1192.217  800.500   1.0000          M.sub.2                              23    239.014   13.881    1.48295 (fluorite)                                                                             L.sub.41                             24    701.943   14.547    1.0000                                               25    -221.419  40.000    1.48295 (quartz)                                                                               L.sub.42                             26    -252.472  0.500     1.0000                                               27    138.449   40.079    1.48295 (fluorite)                                                                             L.sub.43                             28    -253.108  0.500     1.0000                                               29    -249.340  21.997    1.53126 (quartz)                                                                               L.sub.44                             30    313.176   0.499     1.0000                                               31    335.839   13.623    1.48295 (fluorite)                                                                             L.sub.45                             32    22383.397 0.500     1.0000                                               33    94.117    45.000    1.53126 (quartz)                                                                               L.sub.46                             34    63.412    4.289     1.0000                                               35    79.601    40.000    1.48295 (fluorite)                                                                             L.sub.47                             36    775.688   26.439    1.0000                                               <Condition Corresponding Values>                                               β.sub.M1 = -0.828                                                         β.sub.M2 = -2.242                                                         β.sub.G4 = 0.120                                                          ______________________________________                                    

FIG. 24 shows coma for explaining the imaging performance of the 14th embodiment. FIG. 24 shows coma in the meridional and sagittal directions at the center of the ring-shaped view field. A broken curve represents coma at 213 nm, a solid curve represents coma at 217 nm, and a dotted curve represents coma at 221 nm. As can be seen from FIG. 24, the catadioptric reduction projection optical system of the 14th embodiment performs correction of aberration within this range, and has an excellent imaging performance.

The 15th embodiment will be described below with reference to FIG. 25. FIG. 25 shows a light path showing a 15th embodiment of the present invention. As shown in FIG. 25, a light beam from the object surface passes through a first lens group G₁ of positive refractive power, and its light path is bent by a planar reflection mirror M₃. The light beam passes through a second lens group G₂ and is reflected by a first concave reflection mirror M₁ having a magnification slightly smaller than unity magnification. The first lens group G₁ comprises a plano-convex positive lens L₁₁ having a planar surface facing the object surface, a positive meniscus lens L₁₂ having a convex surface facing the object side, and a negative meniscus lens L₁₃ having a convex surface facing the object side. The planar reflection mirror M₃ is disposed between the positive meniscus lens L₁₂ and the negative meniscus lens L₁₃.

The second lens group G₂ is disposed between the first lens group G₁ and the first concave reflection mirror M₁, and comprises a negative meniscus lens L₂₁ having a convex surface facing the first concave reflection mirror M₁ side.

The first lens group G₁ mainly functions to correct distortion and to maintain telecentric characteristics. The second lens group G₂ mainly functions to correct come of high orders generated by the first and second concave reflection mirrors M₁ and M₂. The light beam reflected by the first concave reflection mirror M₁ passes through a third lens group G₃ via the second lens group G₂ to form a primary reduced image I₁.

The third lens group G₃ comprises a positive meniscus lens L₃₁ having a convex surface facing the first concave reflection mirror side, a negative almost plano-concave lens L₃₂ having a concave surface facing the primary image I₁ side, and a positive meniscus lens L₃₃ of weak refractive power having a convex surface facing the primary image I₁ side. The third lens group G₃ functions to correct distortion and curvature of field, and functions as a field lens.

After the light path of the light beam is bent by a planar reflection mirror M₄, the light beam emerging from the third lens group G₃ is reflected by the second concave reflection mirror M₂ and is incident on a fourth lens group G₄ of positive refractive power. The fourth lens group G₄ comprises, in succession from the incident side of a light beam, a biconvex lens L₄₁, a biconcave lens L₄₂, a positive meniscus lens L₄₃ having a convex surface facing the second concave reflection mirror M₂ side, a biconcave lens L₄₄, a biconvex lens L₄₅, a negative meniscus lens L₄₆ having a convex surface facing the second concave reflection mirror M₂ side, and a positive meniscus lens L₄₇ having a convex surface facing the second concave reflection mirror M₂ side. The fourth lens group G₄ forms a secondary image I₂ in a larger reduction scale than that of the primary image I₁. At this time, only part of each of the negative meniscus lens L₁₃ in the first lens group G₁, the planar reflection mirror M₃, and the positive meniscus lens L₃₁ and the negative almost plano-concave lens L₃₂ in the third lens group G₃ is used so as not to shield opposing light paths.

The 15th embodiment has a reduction factor of 0.25 or 1/4 as a whole, and achieves a numerical aperture (N.A.) of 0.45 in a ring-shaped view field centered on a wafer having a radius of 20 mm from the optical axis. The center and spread of wavelengths of a light source used for illumination are λ=217±4 nm.

Data of the 15th embodiment are shown in Table 15 below.

In Table 15, signs of the refractive index and the plane-to-plane distance are inverted by the reflection by the concave reflection mirror. The refractive index of each glass material corresponds to that at the center wavelength (217 nm). The positions of the planar reflection mirrors M₃ and M₄ for bending an optical path are omitted since they are not essential in the optical design.

                  TABLE 15                                                         ______________________________________                                         Data of 15th Embodiment                                                                        Plane-to-                                                            Radius of Plane     Refractive                                           No.   Curvature Distance  Index                                                ______________________________________                                               (Object   183.527   1.0000                                                     Surface)                                                                 1     ∞   37.138    1.53126 (quartz)                                                                               L.sub.11                             2     -339.043  0.500     1.0000                                               3     256.545   17.073    1.53126 (quartz)                                                                               L.sub.12                             4     429.175   155.427   1.0000                                               5     314.370   15.000    1.53126 (quartz)                                                                               L.sub.13                             6     154.417   504.109   1.0000                                               7     -236.577  20.000    1.48295 (fluorite)                                                                             L.sub.21                             8     -369.351  266.233   1.0000                                               9     -799.568  -266.233  -1.0000         M.sub.1                              10    -369.351  -20.000   -1.48295                                                                               (fluorite)                                                                             L.sub.21                             11    -236.577  -491.460  -1.0000                                              12    -216.826  -35.000   -1.53126                                                                               (quartz)                                                                               L.sub.31                             13    -536.198  -34.164   -1.0000                                              14    -1123.930 -15.000   -1.48295                                                                               (fluorite)                                                                             L.sub.32                             15    -199.354  -199.805  -1.0000                                              16    1488.012  -21.214   -1.53126                                                                               (quartz)                                                                               L.sub.33                             17    1000.000  -880.000  -1.0000                                              18    1143.371  802.383   1.0000          M.sub.2                              19    222.215   22.128    1.48295 (fluorite)                                                                             L.sub.41                             20    -929.491  0.500     1.0000                                               21    -1000.000 7.500     1.53126 (quartz)                                                                               L.sub.42                             22    1221.490  0.500     1.0000                                               23    116.974   36.073    1.48295 (fluorite)                                                                             L.sub.43                             24    1474.680  7.516     1.0000                                               25    -407.993  19.063    1.53126 (quartz)                                                                               L.sub.44                             26    852.730   0.782     1.0000                                               27    1302.010  19.232    1.48295 (fluorite)                                                                             L.sub.45                             28    -376.270  0.500     1.0000                                               29    145.377   45.000    1.53126 (quartz)                                                                               L.sub.46                             30    66.088    1.158     1.0000                                               31    71.786    40.000    1.48295 (fluorite)                                                                             L.sub.47                             32    2939.734  15.769    1.000                                                <Condition Corresponding Values>                                               β.sub.M1 = -0.988                                                         β.sub.M2 = -2.008                                                         β.sub.G4 = 0.142                                                          ______________________________________                                    

FIG. 26 shows coma for explaining the imaging performance of the 15th embodiment. FIG. 26 shows coma in the meridional and sagittal directions at the center of the ring-shaped view field. A broken curve represents coma at 213 nm, a solid curve represents coma at 217 nm, and a dotted curve represents coma at 221 nm. As can be seen from FIG. 26, the catadioptric reduction projection optical system of the 15th embodiment performs correction of aberration within this range, and has an excellent imaging performance.

In accordance with the present invention, the catadioptric reduction projection optical system which is simpler in construction than the prior art optical system, and has a larger numerical aperture, a better image-forming ability and a wider illumination field or a wider exposure field is provided. In spite of the large numerical aperture and the wide exposure field, the plane accuracy and the allowance of eccentricity are less severe because of smaller size of the optical elements. Accordingly, it is very useful for a projection optical system for fabricating a semiconductor device. 

What is claimed is:
 1. A catadioptric reduction projection optical system for forming a reduced image of an object, comprising in a light path sequence from the object;a first partial optical system including a first group of lenses having a positive refractive power, a first concave reflection mirror and a second group of lenses having a positive refractive power, for forming a primary reduced image of the object; a second partial optical system including a second concave reflection mirror and a third group of lenses having a positive refractive power, for further reducing the primary reduced image to refocus the image; and a reflection mirror arranged in a light path between said first partial optical system and said second partial optical system for deflecting the optical path.
 2. A catadioptric reduction projection optical system according to claim 1, wherein said first concave reflection mirror has a reduction magnification and said second concave reflection mirror has an enlargement magnification.
 3. A catadioptric reduction projection optical system according to claim 1, wherein a magnification β of said second concave reflection mirror M₂ meets a condition of:

    -2.5<β.sub.M2 <-0.7.


4. A catadioptric reduction projection optical system according to claim 1, wherein a magnification β said first concave reflection mirror meets a condition of:

    -2.0<β.sub.M1 <-0.3.


5. A catadioptric reduction projection optical system according to claim 1, wherein said first group of lenses is arranged in the vicinity of the object functions as a field lens and corrects distortion aberration, and said second group of lenses and said third group of lenses contribute to the formation of the reduced image and function to correct a Petzval sum.
 6. A catadioptric reduction projection optical system according to claim 1, wherein said first concave reflection mirror and said second concave reflection mirror are spherical mirrors, and said second partial optical system has a fourth group of lenses between said second concave reflection mirror and said third group of lenses.
 7. A catadioptric reduction projection optical system according to claim 6, wherein said first group of lenses of said first partial optical system includes a biconvex positive lens and a negative meniscus lens having a convex surface thereof facing the object, said second group of lenses includes a negative meniscus lens having a convex surface thereof faced to said first concave reflection mirror and a positive lens having a stronger radius of curvature on a surface facing said first concave reflection mirror, and said third group of lenses of said second partial optical system includes a positive lens having a stronger radius of curvature on a surface facing said second concave reflection mirror, a meniscus lens having a convex surface thereof facing said second concave reflection mirror and a positive lens having a stronger radius of curvature on a surface facing said second concave reflection mirror.
 8. A catadioptric reduction projection optical system according to claim 6, wherein said first partial optical system has a fifth group of lenses including a meniscus lens having a convex surface thereof facing said first concave reflection mirror.
 9. A catadioptric reduction projection optical system according to claim 8, wherein said first group of lenses includes a biconvex positive lens, a meniscus lens having a concave surface thereof facing the object and a meniscus lens having a convex surface thereof facing the object.
 10. A catadioptric reduction projection optical system for forming a reduced image of an object, including:a first partial optical system having first reflecting means and first refracting means to condense a light beam from the object and form a reduced primary image; and a second partial optical system having second reflecting means and second refracting means to form a further reduced secondary image from said primary image; said first reflecting means having only one concave reflecting mirror, said first refracting means having a lens group of positive refractive power disposed between said object and said concave reflecting mirror; said second reflecting means having only one concave reflecting mirror, said second refracting means having a lens group of positive refractive power disposed between said concave reflecting mirror of said second partial optical system and said second secondary image.
 11. A catadioptric reduction projection optical system according to claim 10, wherein negative Petzval sum created in the concave reflecting mirror of said first partial optical system and the concave reflecting mirror of said second partial optical system is corrected by positive Petzval sum created by the first refracting means of said first partial optical system and the second refracting means of said second partial optical system.
 12. A catadioptric reduction projection optical system according to claim 11, wherein a magnification β_(M2) of the concave reflecting mirror of said second partial optical system meets a condition of:

    -2.5<β.sub.M2 <-0.7.


13. A catadioptric reduction projection optical system according to claim 11, wherein a magnification β_(M1) of the concave reflecting mirror of said first partial optical system meets a condition of:

    -2.0<β.sub.M1 <-0.3.


14. 14. A catadioptric reduction projection optical system according to claim 11, further including a plane reflecting member disposed between the concave reflecting mirror of said first partial optical system and the concave reflecting mirror of said second partial optical system for bending the optical path.
 15. A catadioptric reduction projection optical system according to claim 10, wherein the concave reflecting mirror of said first partial optical system has a reduction magnification, and the concave reflecting mirror of said second partial optical system has an enlargement magnification.
 16. A catadioptric reduction projection optical system for forming a reduced image of an object comprising, in succession from an object side:a first partial optical system including, in succession from the object side, a first lens group of positive refractive power, and a first concave reflection mirror, for forming a primary image of the object; and a second partial optical system including, in succession from the object side, a second lens group, a second concave reflection mirror, and a third lens group of positive refractive power, for re-imaging the primary image.
 17. A system according to claim 16, wherein said third lens group is constituted to satisfy:

    0.05<β.sub.G3 <0.6

where β_(G3) is the magnification of said third lens group.
 18. A system according to claim 16, wherein said first concave reflection mirror is constituted to satisfy:

    -2.0<β.sub.M1 <-0.7

where β_(M1) is a magnification of said first concave reflection mirror.
 19. A system according to claim 16, wherein said second concave reflection mirror is constituted to satisfy:

    -2.5<β.sub.M2 <-0.7

where β_(M2) is a magnification of said second concave reflection mirror.
 20. A system according to claim 16, wherein at least one of said first to third lens groups is constituted by at least two different optical materials, thereby correcting chromatic aberration.
 21. A system according to claim 20, wherein the optical materials include quartz glass and fluorite.
 22. A system according to claim 16, further including at least two reflection mirrors arranged in light paths of said first and second partial optical systems, thereby making an object surface parallel to an image surface.
 23. A system according to claim 22, wherein one of said at least two reflection mirrors is arranged in the light path of said first partial optical system, andthe other of said at least two reflection mirrors is arranged in the light path of said second partial optical system.
 24. A system according to claim 16, wherein at least one of said first and second concave reflection mirrors has a non-spherical reflection surface.
 25. A catadioptric reduction projection optical system for forming a reduced image of an object, comprising:a first partial optical system for forming a primary image of the object; and a second partial optical system for forming a secondary image of the object based on light from the primary image, said first partial optical system having a first lens group of positive refractive power, a second lens group of negative refractive power, and a first concave reflection mirror in succession from a light incident side, and said second partial optical system having a second concave reflection mirror, and a fourth lens group of positive refractive power, wherein a third lens group is disposed in a light path between said first concave reflection mirror and said second concave reflection mirror, said first to fourth lens groups consist of at least one material selected from a group consisting of quartz glass and fluorite, and a magnification β_(M1) of said first concave reflection mirror and a magnification β_(M2) of said second concave reflection mirror meet conditions of:

    -1.0<β.sub.M1 <-0.7

    -2.5<β.sub.M2 <-1.2.


26. A system according to claim 25, wherein a magnification β_(G4) of said fourth lens group meets a condition of:

    0.05<β.sub.G4 <0.3.


27. 27. A system according to claim 26, whereinsaid third lens group has at least one positive lens consisting of quartz glass and at least one negative lens consisting of fluorite, and said fourth lens group has at least two positive lenses consisting of fluorite and at least one negative lens consisting of quartz glass.
 28. A system according to claim 26, whereinsaid second lens group is constituted by a single lens of negative refractive power, and a glass material of said single lens is fluorite. 